Article 106 (b).

Merit Grant in Infant Schools.

BY MRS. MORTIMER,

Lecturer on Kinder-garten at the Home and Colonial Training College, London.

Section II.-Phenomena of Nature.

LESSON-THE SUMMER.

CAN you tell me what part of the year we spoke about last week? Yes, the spring. How many months are there in the spring? What are their names? Can you tell me what comes after the spring? The summer. And how long is the summer? Can you tell me the names of the months? What kind of weather do we have? Yes, it is very hot, and we see the sun for a long time. What kind of days would you say we had? The days are very long, and the nights very short. Yes, when you wake up in the morning you see the sun shining, and when you go to sleep at night it is still light.

Are you glad when the summer comes? Yes, we can keep out of doors then. You are able to have all your games in the open air; and the bright weather makes you feel very happy. Your fathers and mothers are also very pleased to see the summer come. They are able to get out into the fresh air after they have finished their work. Can you tell me some of the things we do in the summer-time? Little children go for nice walks in the parks and fields, they run and jump about, and when they are tired they can sit down on the grass without catching cold. Could you do this in the winter-time? No, we have to go indoors when we want to sit down. What do the big boys do? They play at marbles and tops, and also at cricket. If they are near the water they like to bathe in it, for it is not very cold. Men also like to row the boats on the water, and sometimes boys sail their little ships. Then you can go fishing without catching cold. Yes, and there are many other things we do in the summertime.

Although you can play so much in the open air you must be careful not to get too hot, nor to stand about in the sun without having your hat on, for you are sure to be very ill if you have your head uncovered.

There are other reasons why we like the summer to come. In the summer-time all the things in the gardens and fields grow very fast, and the fruit gets ripe. Can you tell me some of the fruits that grow in the fields and gardens? The apples, pears, plums, cherries. Yes, these all grow on trees. Tell me the names of some that grow on bushes? Yes, currants, gooseberries, raspberries, and strawberries. Well, the raspberries grow on what are called canes, and the strawberries grow on little plants close to the ground. Then we see the corn growing very high, and towards the end of the summer it gets quite ripe. We like to see the golden ears of corn with the sun shining upon them. Can you tell me the name of the corn of which flour is made? It is called wheat. What do we make of flour? It is made into bread. When we see the fields full of good wheat we know we shall have good bread. When the corn is ripe it is cut down, and we say the harvest-time has come. Haymaking should also be referred to.

Then the gardeners are very busy in the gardens. Why? Because the gardens are full of flowers, and they all want looking after. Can you tell me the names of some of the summer flowers? Roses, geraniums, fuschias, marigolds, nasturtiums, sunflowers, sweet peas, mignonette, etc. The warm weather makes these and all other things grow very quickly. Some things, however, which we do not like in the garden give the gardeners a great deal of work. Can you tell what they are? Yes, they are the weeds. Why do we not like them? Because they spoil the garden and prevent the flowers from growing nicely. The other day some little girls told me they had a nice lawn in their garden. What do we call a lawn? A nice plot of grass. Well, what does the gardener have to do

to this? He has to cut it very often. Why? Because it grows so quickly in the warm weather.

In the summer-time you have nice long holidays. Where do some of you go then? To the seaside and into the country. The pleasures of the seaside and country should then be slightly alluded to.

Section III-Scenes of Common Life.

LESSON-THE PARTS OF A HOUSE.

To-day, children, we are going to talk about the different parts of a house, and I want you to tell me the uses of them.

First tell me all the different parts you can think of. The walls, the windows, the doors, the roof, the rooms. That will do. Now, of what are the walls made? They are made of bricks, and sometimes of stone. Of what else are they sometimes made? How many of you have seen wooden houses? Well, then the walls are sometimes made of wood. A little boy says they are made of tin. I think he means of iron. I daresay you have all seen the church not very far from here that is made of iron. That is only put there until the people have enough money to build one of bricks or stone. Why do we build the walls of bricks or stone? To keep out the wet and the cold. Of what other use are the walls? They have to hold the floors, the windows and the doors. Where is the roof of the house? At the top. Of what is it made? Of slates or tiles. Yes, and in the country it is made of straw, etc. We say these kinds of roofs are 'thatched.' Are the roofs generally quite flat? Oh, no, they are slanting. Can you tell me why they are slanting? For the rain to run off. Where does the rain run to? The rain-water runs into the gutters. Where are the gutters? All round the edge of the roof. Yes, and I daresay you have all seen a long pipe running down the wall of the house from the top to the bottom; this pipe carries the water from the gutters into the drains. In the country the people have very large tubs, and the water from the pipe runs into them. This water is very soft and nice for washing. Why do not the people in London do the same? The teacher should briefly explain this to the children.

What do you see on or above the roof? The chimneys. For what are they used? They carry off the smoke from the fires. Where are the fires? Inside the rooms. For what do we use them? To cook our food and to warm ourselves.

When you want to get into the house, what must you do? Wait until the door is opened. When you have entered the house in what part are you? In the passage. Yes, sometimes we call it the hall. What can you see when you are standing in the hall? A number of doors. Where would they lead you? Into the rooms. What else do you see from the hall? The stairs. Where do the stairs lead? To the rooms on the next floor. What do we call the part at the top of the stairs? The landing. If you stand on the landing what do you see? Several doors. What do these open into? Into different rooms. What do you call the stairs leading from the hall to the landing? A flight of stairs. Is there more than one flight of stairs? Yes, there are generally two flights and sometimes more. Well, Mary says there is a flight of stairs in her house leading from the hall down to the kitchen. When you have to go downstairs from the hall to the kitchen, we say the kitchen is in the basement. What do we call the rooms on the first landing? The first floor. And on the second landing? The second floor. So you see in some houses we have a ground floor, a first floor, a second floor, etc.; and then in others we have a floor below the ground floor which we call the basement.

Why do we have doors to our houses and rooms? To keep out the cold and the wet. And for what else? To prevent anybody from walking in when they choose. What do we do when we go out? We lock our doors. Why? So that our house will be quite safe.

If we

were to leave our doors open perhaps some persons, whom we should not like, might come in. Tell me what you call those persons? What do you mean by robbers and thieves? Yes, bad people who get into our houses and take our things away.

Then you told me there were windows in the house. Of what are they made? Of wood and glass. Of what use are they? They let in the light, and at the same time keep out the cold and wet. Why are they made to open and shut? When it is warm weather or when the room is too hot we are able to open the windows and let in the cool air, and when the room is cool enough we can shut them again.

Tell me the names of the different rooms in your house, Harry? The kitchen, the sitting-room, and the bed-room. Who can tell me the names of any other rooms? The scullery. Well, Willie? My uncle has a dining-room. Yes, and some people call another room, the parlour or drawing-room. The children might then be asked the use of each room.

Then we must not forget that your mothers like to find nice large cupboards in the different rooms. Why?

Summary.-The children might write on their slates the names of the different parts of the house, and for a further exercise they might say of what they are made, and for what they are used.

Section IV-Common Employments.
LESSON-THE PORTER.

Now, children, I want you to think of a railway station, and tell me what you can see there. Yes, that is right. Now what men do you see about the station? The porters, the guards, the station-master. Where do you generally see the guard? In the train. How do you know a porter? By the dress he wears. What kind of clothes does he wear? They are of a dark colour, they look thick and strong. On his coat he has rather large buttons, and on his cap there are some letters. Tell me some of the letters you have seen? Harry says he has seen M.R. and D.R. Jack says he once saw G.N.R., and Mary said she saw S.W.R. Well, these letters show which railway the porters belong to. M.R. stands for Metropolitan Railway, D.R. stands for District Railway, and G.N.R. stands for Great Northern Railway. wonder who can tell me for what S.W.R. stands? That is right, it means South Western Railway. What kind of coat does the porter wear? It is a short one, and it is called a jacket. Do the guards and ticket-collectors wear the same kind of clothes? No, they are made of smooth cloth, and they have long coats instead of jackets. One little boy says the porters wear striped jackets; well, they sometimes do in the warm weather, because their other clothes are so thick and warm.

I want you now to tell me some of the things you have seen the porters doing. They sweep the platforms, pick up the pieces of paper, clean the lamps, and when the weather is hot they sprinkle the platform with water. Why do they do this? To keep the stations cool. But the porters do something else. What do they do when the train comes in? They call out the name of the station very loudly. Why? So that the people in the train may know where they are. The porters also call out where the train is going. And what else? They open and shut the carriage-doors and help the people in and out. Then they have to look after the luggage and see that it is right. How can they tell? They read the papers on it. Yes, we call these papers the labels. If your luggage is too heavy for you, the porters will carry it for you.

You see, then, that the porter has a great many things to do and see to. What kind of man ought he to be? He ought to be quick and strong. Why? Because he has to carry heavy luggage, and the train cannot wait long for him. Then he should be kind and civil. Why? Because he has to help people and tell them where to go. Then he must be clean and able to read. Why? Because he has to look at the labels, and he has to label the luggage when you are starting,

Chemistry of the Non-Metallics.

BY EDWARD AVELING, D.Sc. LONDON. [This series of articles, whilst dealing with the subjects required by the University of London for the Matriculation Examination and with those required at the Elementary Stage of the Inorganic Chemistry (Branch X.) Science and Art Department, is intended as a practical guide to the philosophical and systematic study of the non-metallics.]

CHAPTER V.-HYDROGEN (continued). VALENCY. ICE. WATER. STEAM. LATENT HEAT. E. MIXTURES.-None is known.

COMPOUNDS. (a) General.-Hydrogen combines with every one of the non-metals, except, as far as is known, boron. A list of symbols and names of some of the conpounds resulting follows:

HF

H2S

H3P

H'Si ...

(hydrobromic acid).

iodide (hydriodic acid).

fluoride ,, (hydrofluoric acid).
sulphide,, (sulphuretted hydrogen).
phos-

phide, (phosphuretted hydrogen). silicide ,, (siliciuretted hydrogen).

From this list two principles may be learnt. Note that one atom of hydrogen combines with one atom of each of the following elements: hydrogen, chlorine, bromine, iodine, fluorine; that two atoms of hydrogen combine with one of each of the following: oxygen and sulphur; that three atoms of hydrogen combine with one atom of nitrogen and of phosphorus; and that four atoms of hydrogen combine with one atom of carbon and with one atom of silicon.

An element I atom of which unites with I atom of hydrogen =a monad; μovos (monos)=1. An element 2 atoms of which unite with ratom of hydrogen =a dyad ; dúo (duo)=2. An element 3 atoms of which unite with I atom of hydrogen =a triad; Tpeis (treis)=3. An element 4 atoms of which unite with I atom of hydrogen tetrad; TETTаpa (tettara)=4. Thus hydrogen, chlorine, fluorine are monads; oxygen and sulphur are dyads; nitrogen and phosphorus are triads; carbon and silicon are tetrads.

These names, monad, dyad, triad, tetrad, express what is called the valency of an element. Some elements, however, do not unite with hydrogen, and their valency has to be determined by noting how many atoms of hydrogen they replace it. Reference to the equation that represents the formation of hydrogen from water and potassium (see page 260) will show that one atom of potassium replaces one atom of hydrogen. H2O or HHO is the symbol of water; KHO that of potash.

Reference to the equation that represents the formation of hydrogen from zinc and sulphuric acid will show that one atom of zinc replaces two atoms of hydrogen. H SO is the symbol of sulphuric acid. ZnSO4 that of zinc sulphate.

Hence the full definition of a monad is an element, one atom of which combines with or replaces one atom of hydrogen; of a dyad is an element, one atom of which combines with or replaces two atoms of hydrogen; of a triad, an element, one atom of which combines with or replaces three atoms of hydrogen; and of a tetrad, an element, one atom of which combines with or replaces four atoms of hydrogen.

There are higher valencies than the four just named. Some few elements act as pentads and hexads. The majority of the sixty-three elements are dyads. If, there fore, a list of the chief monads, triads, tetrads is given, the student will remember that all the elements with which he has to do, not in that list, are dyads.

Monads. Hydrogen, chlorine, bromine, iodine, fluorine......Potassium, sodium, silver.

Triads.

Finally, the bulb, F, most to the right, is, at first, empty, and the tube beyond, C, contains calcium chloride. This bulb and tube must also be weighed. Before any heat is applied to the copper oxide, expel all air by a current of hydrogen evolved from the zinc and sulphuric acid. Then

Tetrads.

Carbon, silicon...... Platinum, tin.

The second principle to be learnt from the list of symbols and compounds has to do with nomenclature. Only two elements are concerned in each compound represented there, whatever may be the number of atoms of each element present. The name of each compound is a double name. One word of the name is 'hydrogen.' This tells us that the element hydrogen is the positive electric constituent or basylous radicle of the compound. The other word tells us that some other element is the negative electric constituent or chlorous radicle, and this second word always ends in 'ide.' A like method is adopted in naming every compound of two elements. A few more symbols and names are given :

hydrogen, passing over the red-hot copper oxide, unites with the oxygen of that compound and forms hydrogen oxide, or steam. This condenses in the second bulb or in the calcium chloride tube beyond. Copper is left in the bulb, E, over the flame. Weigh this bulb at the end of the experiment. The loss of weight as compared with the weight before the experiment tells the weight of the oxygen in the water that is formed. Weigh the two last pieces of apparatus, F and G, most to the right. The gain in weight tells us the whole weight of the water formed. The difference between these two numbers is the weight of the hydrogen in the water that is formed. This is the synthetical method of determining the composition of water. ou (sun) = together, Onois (thesis)=a placing. Synthesis is, therefore, the putting together of bodies to form a compound.

No matter how many times this experiment or that of the analysis of water is repeated, the result is the same, if the experiments are conducted with care. Hence we are led to the first great law of chemical combination, that chemical compounds always contain their components

Of the long list given on page 494, only the second and third will be studied in connection with hydrogen. The others will be studied under the account of the element that is combined in each case with hydrogen.

(B) Special. Hydrogen oxide.-(a) Symbol, HO.

(b) Weight-number, 18. (c) Preparation.-In the form of water this compound is so prevalent that its preparation is unnecessary, save as an interesting chemical experiment.

(1) Laboratory Method.-Burn hydrogen. This gas combining directly with oxygen, hydrogen oxide results. (2) Symbols.-- 2H2 + O2 = 2H2O. 36. 4 vols. 2 vols. 4 vols.

(3) Weight-numbers.- 4 + 32

Another preparation of hydrogen oxide is of interest also as showing the exact composition (by weight) of that compound.

(1) Laboratory method.-Arrange apparatus as shown in Fig. 16. The first bottle to the left, A, is one for the evolution of hydrogen by the action of sulphuric acid on zinc. The two succeeding bent tubes are partly filled with calcium chloride (CaCl2). This substance absorbs any moisture that may be mixed with the escaping hydrogen. The fourth piece of apparatus is another bottle containing sulphuric acid. Thus, when the hydrogen gas passes, it is delivered dry and pure into the bulb, E, below the burner. In this bulb is some copper oxide (CuO), carefully dried by heat, and carefully weighed.

QUESTIONS ON THE SYNTHESIS OF WATER (for

oxide?

solution).

42. What weight of water will be formed by the passage of 4 grams hydrogen over an unlimited quantity of red-hot copper .36 grams. 43. Required a litre of water. What weight of copper oxide, and what volume of hydrogen are needed?

4388 grams; 1244 litres. This same compound, hydrogen oxide, is formed whenever any substance containing hydrogen as one of its elements is burned. If a bright glass is held over a burning candle or over a paraffin lamp, steam is found to be deposited on it. The tallow or wax of the candle has for one of its constituents hydrogen, and this gas joining with the oxygen of the air forms hydrogen oxide.

(d) Properties.-Hydrogen oxide exists in three forms -the solid ice, the liquid water, the gas steam.

(a) Ice.-1. Condition.-Solid; melting at o°C.

2. Effect on the Senses.-Hard, brittle, tasteless, odourless, translucent.

3. Specific gravity.-Lighter than water, with which, like all solids, it is compared. Taking the specific gravity of water as I that of ice is 9175. Hence, when water freezes, expansion takes place. This expansion, when water becomes ice, is the cause of the bursting of water-pipes in houses. The pipes, if full of water, burst when the frost comes, but the discovery of the mischief is made when the thaw sets in, and, the ice melting, the water flows through the flaws. This expansion is also the great agent in the disintegration of rocks. If the crevices of a rock are filled with water when the frost comes, the expansion caused by the water as it turns into ice breaks up the rocks. The lightness of ice as compared with water also explains the fact that ice floats on water.

4. Solubility.-Not soluble in water.

5. Relation to Combustion.-Not combustible.

6. Specialties. When ice becomes water, a larger quantity of heat disappears than when any other solid is changed into its corresponding liquid. Whenever by the application of heat a solid is converted into a liquid heat disappears. Ice, e.g., melts at o°C. But the temperature of a mass of ice to which heat is applied does not rise beyond o° until all the ice is turned into water. Thus, the heat of the fire applied to the ice melts it, without raising its temperature. The heat that was perceptible by its action upon the thermometer no longer affects that instrument. The mass of ice at o° has become a mass of water at o°. The heat has been rendered potential or latent. As soon as all the ice has become water, the continued application of heat will cause the temperature of the water to rise.

In the melting of every solid, heat becomes potential or latent. It has the power to do work, but is not doing work. It is not, for the time being, kinetic heat. Kinos (kinesis)= movement. In the case of ice, a larger quantity of kinetic heat is rendered potential than in the conversion of any other solid into its corresponding liquid.

To understand how much heat passes from the kinetic to the potential condition when ice becomes water, the meaning of the phrase heat-unit must be explained. A heat-unit, or thermal unit, or gram-degree, is the quantity of heat necessary to raise the temperature of a gram of water from o° to 1°. Note that this unit quantity of heat is by no means the same as a degree of temperature. These two quite different things must not be confounded. 20 grams of water raised from o° to 1° require 20 heat-units.

10°

200

100°

To convert I gram of ice at o° into 1 gram of water at 0°, 79°2, or, approximately, 80 heat-units are required. Hence I gram of ice at o° mixed with 1 gram of water at 80°, or mixed with 2 grams of water at 40°, or mixed with 80 grams of water at 1°, or mixed with 10 grams of water at 8°, would result in 2, 3, 81, II grams of water, `respectively, at o°.

Some examples on the potential heat of water will be given after the consideration of water itself.

(8.) Water.-1. Condition.-A liquid freezing at o°, boiling at 100. The freezing-point and boiling-point of water are respectively o° and 100°, only under normal conditions. With varying external circumstances they vary. The freezing-point is not always o°. By cooling water, out of contact with air and kept perfectly still, a temperature of -10° or - 15° has been reached before the water becomes ice. The slightest shaking of the water causes it suddenly to turn into ice, the temperature rising at the same time to o°.

sure.

The freezing-point alters also with variation of presWhen water turns into ice, expansions occurs. Thus I vol. of water at o° becomes 1'09082 of ice. Anything that retards this expansion will make the conversion of water into ice more difficult. Increase of pressure will retard the expansion. Hence, if the pressure on the water is increased, solidification of the water is rendered more difficult, and a lower temperature (or in ordinary language, more cold') is required. The melting-point is lowered '0075° for every additional pressure equivalent to that of a column of mercury 760 mm in height.

The boiling-point is not always 100°. It may be either higher or lower than 100°. The chief circumstances affecting the boiling-point are pressure, the nature of the vessel in which the water is placed, and the presence of salts in solution in the water.

i. Pressure.-Increase of pressure raises the boilingpoint. Diminution of pressure lowers the boiling-point. When water becomes steam, as it passes off it has to overcome the pressure of the air upon the surface of the water. Any increase of that pressure makes it harder work for the water to become steam, and a higher temperature (or, in ordinary language, ' more heat ') is required. 27 mm., measured in mercury, increase or diminution of the pressure on the water causes the boiling-point to rise or fall 1o.

ii. The Nature of the Vessel.—Water in a vessel made of some material to which the water adheres will boil at a higher temperature than in a vessel made of a material to which the water does not adhere. Adhesion between the water and the sides of the vessel tells against the passage of the water into the state of steam.

iii. Presence of Salts in Solution in Water.-As in the preceding case, adhesion of water to the particles that it holds in solution tells against the water passing off as steam. Distilled water boils, therefore, at a lower temperature than water containing matters in solution. 2. Effect on Senses.-Pure water is without taste or odour, colourless and transparent, unless seen in large quantity.

3. Specific Gravity.-Since water is taken as the standard of comparison for liquids and solids, its own specific gravity is 1. Water is about 11,937 times as heavy as hydrogen, say, 11,940. It is 825 times as heavy as air.

4. Solubility.

The

5. Relation to Combustion.-Not combustible. 6. Specialties. It is the universal solvent.' student should try the effect of distilled water on common salt, which is readily soluble, plaster of Paris (slightly soluble), cbalk (insoluble). He should, after making a solution of common salt or of common 'soda,' (really, sodium carbonate), and of copper sulphate, evaporate each of the three solutions and observe the dissolved solids crystallise out as the solvent water passes off in the form of steam.

As a rule, the higher the temperature of the water, the more does it dissolve of the soluble substance, if the latter is a solid. In making a solution of a solid body, the force of cohesion between the particles of the solid has to be overcome. The adhesion between the water and the solid particles is in opposition to this cohesion and overcomes it when the solution is made. Heat, however, helps adhesion as it tends to separate the particles of the solid one from the other, and tells against the cohesion.

On the other hand, gases are less soluble in hot water than in cold. In gases the force of cohesion is nil. The particles of a gas are already repelling one the other.

Hence a rise of temperature in this case tells against the adhesion between the water and the gas.

From the experiments on page 260 and page 378 it will be seen that water is decomposed by sodium or potassium at the ordinary temperature, and by iron at a red heat. Other metals, such as copper and platinum, do not decompose water under any circumstances. Water combines with certain metallic compounds with great evolution of heat. Thus, if it is poured on quicklime (CaO), it unites with that compound to form calcium hydrate, and in the union much heat is evolved. CaO + H2O == Ca (HO)2 40+16+2+16 = 40+2 (1 + 16)

The effect of heat on water is peculiar. The majority of bodies when heated expand. If water at of has its temperature raised, instead of expanding it contracts until the temperature of 45° is reached. Then, if the temperature is still raised, the water behaves like liquids generally and expands regularly. Hence, if water at 45° is either cooled or heated it expands. This temperature is therefore called the point of maximum density of water. From this remarkable property of water it follows that when the surface of a mass of water, such as a lake, is cooling from the ordinary temperature of the air (say, 15°) downwards to 45°, that surface becoming cooler than the underlying regions of water is heavier than these, and constantly fails down. The lighter, hotter, originally underlying water, rising takes its place, and in its turn is cooled, becomes heavy, and falls. But when the temperature of 45° is reached, the upper layer of water begins to expand, is lighter than the water beneath it, and floats at the top. This it continues to do as the temperature falls from 4'5° to oo, and then the surface water freezing, and again expanding as as it freezes, the ice, a non-conductor of heat, is at the top of the lake and warmer water underneath.

The next special point to be considered in regard to water is of the same nature as that on which I dwelt for some time in considering ice. When water becomes steam a larger quantity of heat disappears than when any other liquid is changing into its corresponding gas. Whenever, by the application of heat, a liquid is converted into a gas, heat disappears. Water, e.g., boils at 100°. But the temperature of a mass of water to which heat is applied does not rise beyond 100° until all the water is turned into steam. Heat is rendered potential or latent. As soon as all the water has become steam, the continued application of heat will cause the temperature of the steam to rise.

The number of heat units that are converted from the kinetic to the potential condition when I gram of water at 100° becomes 1 gram of steam at 100% is 536.

Ir is a great advantage to both teacher and scholar that the examination of the class-subjects' is generally oral and not written. With such young minds as we have to deal with, where the knowledge acquired is always far in advance of the ability to express it, it is an injustice to the teacher and a discouragement to the pupil to insist upon a written examination. Moreover, such a method of testing leads, in some cases, to mere cram, and to the learning by memory of certain answers to a few stereotyped questions; by

which means, the whole purpose of science teaching is entirely frustrated. Indeed I have always felt sorry that the examination of even the specific subjects is by means of written answers only; in these cases, however, as the grant is given upon individual passes, I suppose an exclusively oral examination would be impracticable.

I would here impress upon the teacher the advisability of always performing the proposed experiment by himself before the class meets. I so often find that where this is not done the experiment is a complete failure, and the class is thrown into confusion.

The following simple notes form a continuation of the syllabus which appeared in the October issue of this magazine.

LESSON XVI.-THE CHEMISTRY OF WATER (a).

It is an oxide-the When water is sepa

Water exists in nature in the three states-solid, liquid, and gaseous. In all three states, it has, of course, the same composition. protoxide of hydrogen, H2O. rated into its elements, these appear as the two gases, hydrogen and oxygen. Here refer to a previous lesson for the main characters of those gases; and contrast those characters with the properties possessed by the compound. There are two volumes of H to one of O; or sixteen parts by weight of oxygen to two of hydrogen. Water may be analysed by (a) heat, (b) by electricity, (c) by displacement.

This

First by heat. It was the opinion of Captain Shaw, of the London Fire Brigade, that when water was poured into an intensely hot part of a burning building the fire blazed up with greater fierceness. The water was, in fact, decomposed; giving rise to hydrogen, which at once inflamed, and to oxygen, which supported the combustion. Picture these effects before the boys. If possible, perform the following experiment. Get a piece of -inch iron pipe (gas pipe) two feet long. Weigh out exactly two ounces of very small iron brads, or, preferably, some clean iron turnings. Stuff them into the middle part of the pipe. can be done by ramming them from both ends of the pipe with two pieces of iron rod. Fix into each end of the pipe, by means of perforated corks, a length of glass tubing. Fit the free end of one tube into the neck of a flask containing water to be boiled. Let the free end of the other tube dip under a collecting jar at the pneumatic trough. Light at least two Bunsen burners, and place them under the middle part of the iron tube, so as to make it, and the iron turnings within it, red hot. Boil the water in the flask, over a spirit lamp. The invisible water-vapour from the flask passes into the iron pipe and over the redhot iron turnings: these absorb the oxygen from the H2O, and form an oxide of iron-the black oxide, Fe3O4; while the remaining hydrogen passes out of the iron pipe and may be collected in the usual way and tested.