tating chemical calculations, to reduce the units to the lowest term, consistent with the avoidance of fractions; we therefore say that the atoms in a molecule of free hydrogen act in chemistry as two separate groups, each of a minimum relative weight of 1, whilst those in a molecule of free mercury act as one undivided group of the relative weight 200. But to what number of atoms the I and 200 correspond respectively no chemist knows.

To show how intimately chemistry and electricity interlock, I may here remark that one of the latest theories in chemistry renders such a division of the molecule into groups of electro-positive and electro-negative atoms necessary for a consistent explanation of the genesis of the elements. This is so important that I may be excused for digressing a little into this development of theoretical chemistry.

Genesis of the Elements.

It is now generally acknowledged that there are several ranks in the elemental hierarchy, and that besides the well-defined groups of chemical elements, there are underlying sub-groups. To these sub-groups has been given the name of meta-elements. The original genesis of atoms assumes the action of two forms of energy working in time and space-one operating uniformly in accordance with a continuous fall of temperature, and the other having periodic cycles of ebb and swell, and intimately connected with the energy of electricity (Fig. 30). The centre of this creative force in its journey through space scattered seeds or sub-atoms that ultimately coalesced into the groupings known as chemical elements. At this genetic stage the new born particles vibrating in all directions and with all velocities, the faster moving ones would still overtake the laggards, the slower would obstruct the quicker, and we should have groups formed in different parts of space. The constituents of each group whose form of energy governing atomic weight was not in accord with the mean rate of the bulk of the components of that group, would work to the outside and be thrown off to find other groups with which they were more in harmony. In time a condition of stability would be established, and we should have our present series of chemical elements each with a definite atomic weight-definite on account of its being the average weight of an enormous number of sub-atoms or meta-elements, each very near to the mean. The atomic weight of mercury, for instance, is called 200, but the atom of mercury, as we know it, is assumed to be made up of an enormous number of sub-atoms, each of which may vary slightly round the mean number 200 as a

centre.

We are sometimes asked why, if the elements have been evolved, we never see one of them transformed, or in process of transformation, into another? The question is as futile as the cavil that in the organic world we never see a horse metamorphosed into a cow. Before copper, e.g., can be transmuted into gold it would have to be carried back to a simpler and more primitive state of matter, and then, so to speak, shunted on to the track which leads to gold.

This atomic scheme postulates a to and fro motion of a form of energy governing the electrical state of the atom. It is found that those elements generated as they approach the central position are electro-positive, and those on the retreat from this position are electro-negative. Moreover the degree of positiveness or negativeness depends on the distance of the element from the central line; hence calling the atom in the mean position electrically neutral, those sub-atoms which are on one side of the mean will be charged with positive electricity, and those on the other side of the mean position will be charged with negative electricity, the whole atom being neutral.

This is not a mere hypothesis, but may take the rank of a theory. It has been experimentally verified as far as possible with so baffling an enigma. Long-continued research in the laboratory has shown that in matter which has responded to every test of an element, there are minute shades of difference which have admitted of

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selection and resolution into meta-elements, having exactly the properties required by theory. The earth yttria, which has been of such value in these electrical researches as a test of negatively excited atoms, is of no less interest in chemistry, having been the first body in which the existence of this sub-group of meta-elements was demonstrated.

Conclusion.

I frankly admit I have by no means exhausted the subject which daily and nightly fills my thoughts. I have ardently sought for facts on which to base my theory. I have struggled with problems which must be conquered before we can arrive at exact conclusions-conclusions which, so far as inorganic Nature is concerned, can only be reached by the harmonious interfusion-not confusion -of our present twin sciences, electricity and chemistry. of this interfusion I have just endeavoured to give you a foretaste. In elaborating the higher physics, the study of electrical phenomena must take a large, perhaps the largest, share.

We have invaded regions once unknown, but a formidable amount of hard work remains to be completed. As we proceed we may look to electricity not only to aid, as it already does, our sense of hearing, but to sharpen and develop other powers of perception.

Science has emerged from its childish days. It has shed many delusions and inpostures. It has discarded magic, alchemy, and astrology. And certain pseudo-applications of electricity, with which the present Institution is little concerned, in their turn will pass into oblivion.

There is no occasion to be disheartened at the apparent slow pace of elemental discovery. The desponding declare that if Roger Bacon could re-visit "the glimpses of the moon" he would shake his head to think we have got no further, that we are still in a haze as to the evolution of atoms. As for myself I hold the firm conviction that unflagging research will be rewarded by an insight into natural mysteries such as now can scarcely be conceived. Difficulties, said a keen old statesman, are things to be overcome, and to my thinking Science should disdain the notion of Finality. There is no stopping half way, and we are resistlessly driven to ceaseless inquiry by the spirit "that impels all thinking things, all objects of all thought, and rolls through all things."

DETERMINATION OF WATER IN
SUPERPHOSPHATES.*

By JULIUS STOKLASA.
(Continued from p. 101).

IF the phosphoric anhydride corresponding to the free phosphoric acid is deducted from the 35.8 per cent P2O5 found, we have 29.2 per cent P2O5 corresponding to the 51.8 per cent of the undecomposed monocalcium phosphate.

In this case the determination of the free phosphoric acid and the monocalcium phosphate by titration with uranium acetate are not accurate, and the results are only approximations, as, by boiling the acid liquid (the solution of uranium acetate used having been as usual acidulated), a small part of the pyrophosphate is converted into orthophosphate.

According to theory the phosphoric acid is present in the solution in the following form :

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The results above indicated give an interesting explanation of the processes during the desiccation of monocalcium phosphate in a quite new direction. Birnbaum certainly recognised the normal calcium pyrophosphate and free phosphoric acid, but he nowhere mentions having found metaphosphate and monocalcium pyrophosphate. He considers that the decomposition takes place as follows:

2[CaH4(PO4)2+H2O] = Ca2P2O7+2H3PO4+3H2O. The decomposition cannot take place in this manner, since by the continued action of the temperature monocalcium pyrophosphate is formed from pyrophosphate and free phosphoric acid.

S. Drewsen, who examined the transformations of superphosphates at higher temperatures, does not mention the formation of normal calcium pyrophosphate and metaphosphate. He merely observed that a considerable quantity of monocalcium pyrophosphate is formed even at 100°. But this phenomenon, as I will show below, is occasioned by other factors, and not merely by temperature. He suggests, therefore, that the aqueous solution of superphosphates on analysis should be boiled with nitric acid, as we cannot know if the superphosphate in question has been artificially dried at a high temperature. From the tabular conspectus in which he summarises the results of his experiments, it is seen that the quantity of the phosphoric acid soluble in water remained unaltered even in drying the superphosphates at 300°, for if the aqueous solution of such a dried superphosphate was boiled in nitric acid, the same quantity of phosphoric was found as in the original sample. Drewsen does not, indeed, mention the composition of the superphosphates which he examined, but it is evident from his memoir that he means the soluble phosphoric acid which appears in superphosphates as monocalcium phosphate. He is thus in a serious error, for his results cannot be applied to superphosphates, which contain the soluble phosphoric | acid chiefly in the state of monocalcium phosphate.

The author repeated the experiments with superphosphates which contained 18 per cent of soluble phosphoric acid (17 per cent as monocalcium phosphate and I per cent as free phosphoric acid), and on drying for four hours at 120°, he observed great losses of soluble phosphoric acid. Slightly different results are reached if free phosphoric acid is found in the superphosphates in addition to monocalcium phosphate. Drewsen's results may be ex. plained on the supposition that he operated upon superphosphates containing at least 80 per cent soluble phosphoric acid in the state of free acid. At high temperatures the free phosphoric acid, or that liberated by decomposition, reacts upon the normal calcium pyrophosphate so as to form monocalcium pyrophosphate:

Ca2P207+2H3PO4=2CaH2P207+ H2O.

The author has proved this reaction. Chemically pure calcium pyrophosphate (Ca2P2O7+4H2O) was prepared from calcium chloride and sodium pyrophosphate. The analysis showed :

(Calculated). 43'56 per cent. 34'35 "" 22.09

A mixture of 2 grms. pyrophosphate and 1'202 grms. phosphoric acid was dried for ten hours in a platinum capsule at 200°. The monocalcium pyrophosphate formed was placed in a litre flask which was filled with water up to the mark. After shaking for an hour, the solution became slightly turbid, and contained free phosphoric acid only in traces. There was found in the solution monocalcium pyrophosphate (without heating with nitric acid) and 4 per cent of phosphoric acid; after the solution had been heated with nitric acid, there were found 56'08 per cent of phosphoric acid by the molyb. denum method. In our case there was first formed monocalcium phosphate, which afterwards loses water and passes into monocalcium pyrophosphate.

If we dry monocalcium phosphate at 150° for longer than an hour, we do not find the quantity of free phosphoric acid which corresponds to the monocalcium phosphate taken. This phenomenon led to the thought that the decomposition is different. On examining the aqueous solution, there was found a large quantity of monocalcium pyrophosphate. The author proved by a number of experiments that not merely the temperature reached, but the time during which the desiccation formation of monocalcium pyrophosphate. is prolonged at 150°, a higher has great influence on the

(To be continued).

LONDON WATER SUPPLY.

REPORT ON THE COMPOSITION AND QUALITY OF DAILY
SAMPLES OF THE WATER SUPPLIED TO LONDON
FOR THE MONTH ENDING JANUARY 31ST, 1891.
By WILLIAM CROOKES, F.R.S.;
WILLIAM ODLING, M.B., F.R.S., F.R.C.P.,
Professor of Chemistry at the University of Oxford;
and C. MEYMOTT TIDY, M.B., F.C.S., Barrister-at-Law,
Professor of Chemistry and of Forensic Medicine at the London
Hospital; Medical Officer of Health for Islington.

To GENERAL A. DE COURCY SCOTT, R.A., Water Examiner, Metropolis Water Act, 1871. London, February 7th, 1891. SIR,-We submit herewith the results of our analyses of the 142 samples of water collected by us during the past month, at the several places and on the several days indi. cated, from the mains of the seven London Water Com. panies taking their supply from the Thames and Lea. In Table I. we have recorded the analyses in detail of samples, one taken daily, from January 1st to January 31st inclusive. The purity of the water, in respect to organic matter, has been determined by the Oxygen and Combustion processes; and the results of our analyses by these methods are stated in Columns XIV. to XVIII.

We have recorded in Table II. the tint of the several samples of water, as determined by the colour-meter described in a previous report.

In Table III. we have recorded the oxygen required to oxidise the organic matter in all the samples submitted to analysis.

Of the 142 samples examined, 131 were found to be clear, bright, and well filtered, I being recorded as "very slightly turbid," and 10 as " slightly turbid."

As a consequence of the impracticability, during the prolongation of the frost, of obtaining samples of water from some of the standpipes, the record of analytical results included in this Report is more defective than in any that we have hitherto made. Samples of water were occasionally still met with manifesting the evanescent smoky taste spoken of and considered in our previous Report for December; but the analytical results obtained during the first three weeks of the month of January, and ecorded in our present Report, continued to be, except for two instances occurring of slight turbidity, entirely

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5. Specimens of granulated gun cotton, 1876. 6. Specimens of compressed gun-cotton, Abel's system. 7. Gun-cotton slab fired through from a Martini-Henry rifle, without being exploded.

8. Gun-cotton slabs perforated by the electric discharge without ignition.

9. Explosion vessel used in researches on gun-cotton, 1865-1868.

10. First explosion vessel used in Abel and Noble's researches on fired gunpowder, &c., 1871-1880. Note.-Largest powder-charge exploded in the vessel, 21lb.; pressure developed, 43 tons per sq. in.; largest gun-cotton charge exploded, 14 oz. In larger vessels of the same model, 22 lbs. of powder have been exploded, and gun-cotton has been detonated with developments of nearly 70 tons pressure per sq. in. 11. Vacuum bomb used in researches on the combustion of gunpowder and gun-cotton in rarefied atmospheres, 1867.

12. Specimens of " cordite," the new smokeless powder. 13. Photographs showing the 6-in. quick-firing gun, fired with black powder and with cordite (smokeless powder).

(Exhibited by Sir F. A. Abel).

SIR HENRY ROSCOE, M.P., F.R.S.,
President, 1880-1882.

A complete series of specimens of vanadium compounds :

Potassium Vanadium

Vanadium ore. Roasted ore. Ammonium vanadate. Vanadium pentoxide. Vanadium trisulphide, disulphide, and pentasulphide. Silver hypovanadate. Sodium hypovanadate. Hypovanadic tetrachloride and disulphate. Lead hypovanadite. Aqueous solutions of vanadium di oxide, trioxide, tetroxide, pentoxide, dichloride, trichloride, tetrachloride, and vanadyl trichloride. Divanadyl monochloride. Lead metavanadate. Ammonium metavanadate. Vanadium mononitride, trioxide, pentoxide, silicon alloy, and platinum alloy. Vanadous sulphate. Vanadium oxidibromide and trichloride. Vanadyl trichloride. Vanadium tetrachloride (decomposed) and dichloride. anhydrovanadate and anhydrochromate. metal, pentoxide, and nitride. Barium hypovanadate. Vanadic vanadate. Ammonium magnesium phosphate (from Berzelius's vanadium). Metavanadic acid. Sodium anhydrovanadate. Ammonium hypovanadate. Hypovanadic hydrate. Thallium tetravanadate, decakaivanadate, and hexakaivanadate. Silver octakaivanadate. Metavanadic acid. Ammonium vanadate and vanadite. Vanadium sesquioxide. Artificial vanadinite. Ammonium metavanadite. Sodium orthovanadite. Silver orthovanadite. Sodium orthovanadite (fused mass) and pyrovanadate. Pyrovanadate of lead. Sodium octavanadate. Barium pyrovanadate. Silver pyrovanadate. Vanadyl dichloride. Calcium divanadate. Sodium vanadate

vanadite.

(Exhibited by Sir H. E. Roscoe).

J. H. GILBERT, LL.D., F.R S.,
President 1882-1883.

Dr. Gilbert, having been engaged with Sir J. B. Lawes in the conduct of the Rothamsted Investigations from 1843 up to the present time, sends the following illustra. tions of some of the lines of inquiry undertaken :

Apparatus used in an investigation by Messrs. Lawes, Gilbert, and Pugh, in the years 1857, 1858, 1859, and 1860, to determine whether plants assimilate free or uncombined nitrogen. The plants were grown in ignited pumice or soil (with plant-ash added), either with no other supply of combined nitrogen than that contained in the seed sown, or with the addition of known and limited quantities of combined nitrogen; and they were supplied with washed air, and washed carbonic acid. The conditions of growth were, therefore, those of sterilisation; and there was, under such conditions, no gain from free

nitrogen, in the growth of either Gramineæ, Leguminosa, or other plants.

Plate of Gramineous plants grown in 1857 and 1858; and coloured photograph, of coloured scale-drawings, of Leguminous plants grown in 1860.

Three enlarged Photographs, of Leguminous Plants grown in Experiments in 1889, on the Question of the Fixation of Free Nitrogen; in some cases with sterilisation, and in others with microbe-seeding of the soil. With suitable microbe infection of the soil there was abundant formation of the so-called "Leguminous nodules" on the roots of the plants; and there was, coincidently, very considerable fixation of free nitrogen. The evidence at present at command points to the conclusion that the free nitrogen is fixed in the course of the development of the organisms within the nodules, and that the resulting nitrogenous compounds are absorbed and utilised by the higher plant.

Coloured Drawing, by Lady Lawes, of the Rothamsted Rain gauges. For the purpose of accurate measurement of the rain, and of obtaining sufficient quantities for analysis, a large gauge of one-thousandth of an acre area has been in use since the beginning of 1853; also an ordinary funnel-gauge of 5 inches diameter; and these are represented in the drawing. An 8-inch "Board of Trade" copper-gauge has also been in use since January, 1881. The funnel portion of the large gauge is constructed of wood lined with lead; the upper edge consisting of a vertical rim of plate glass, bevelled outwards. The rain is conducted by a tube into a galvanised iron cylinder underneath, and when this is full it overflows into a second cylinder, and so on into a third and fourth, and finally into an iron tank. Each of the four cylinders holds rain corresponding to half an inch of depth, and the tank an amount equal to 2 inches. Each cylinder has a gaugetube attached, graduated to read to o'002 inch, but which can be read to o'oor inch. Small quantities are transferred to a smaller cylinder with a gauge-tube graduated to 0001, or one-thousandth of an inch.

Coloured Drawing, by Lady Lawes, of the Rothamsted Drain-guages. The three "drain-gauges," each of one

The

thousandth of an acre area, for the determination of the quantity and composition of the water percolating respectively through 20 inches, 40 inches, and 60 inches depth of soil (with the subsoil in its natural state of consolidation), have been in use since September, 1870,that is, for a period of more than twenty years. gauges were constructed by digging a deep trench along the front, gradually undermining at the depth required, and putting in plates of cast-iron (with perforated holes), to support the mass. The iron plates were then kept in place by iron girders, and the ends of the plates and of the girders supported by brickwork on three sides. Trenches were then dug bit by bit round the block of soil, which was then enclosed on each side by walls of brick laid in cement. Below the perforated iron bottom a zinc funnel, of the same area as the soil, was finally fixed, and the drainage water is collected and measured in galvanised iron cylinders, with gauge-tubes, as in the case of the rain.

Photograph of a case (now in the Science Museum, South Kensington), illustrating the influence of different manures on the botanical composition of the Mixed Herbage of Permanent Grass-land.

A set of bound volumes of Rothamsted Memoirs, &c., published 1847 to 1890, inclusive. Also the annual "Memoranda" for 1890.

Book of Drawings and Plans of the "Lawes Testimonial Laboratory," Rothamsted, Herts.

(Exhibited by Sir J. B. Lawes and Dr. Gilbert.)

W. H. PERKIN, Ph.D., F. R.S.,

President, 1883-1885.

Dinaphthylguanidine.

Bromacetic acid. Dibromacetic acid. Dibromacetamide.