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CHEAP GLASS HYDROMETER.

mersed, and more easily cleaned. It may be admitted, on the other hand, that its fragility is a disadvantage, but, with tolerable care, it will last for years, and, in case of being broken, the weights, scale, and stem, may all (except, perhaps, the balance weight) be used in making another. I am, Sir, Yours respectfully,

J. S. M.

The Hydrometer is made of glass, excepting the scale, which is of brass, and the stem, which is of hardened steel-wire, about 1-35th of an inch in diameter; load the lower bulb of the instrument with small shot, nearly sufficient to sink the instrument to its neck in water; then fix the stem into the neck temporarily, by running it through a cork made to fit; put the instrument again into water, and load the scale until it sinks to the middle of the stem. The weight in the scale added to the weight of the instrument will equal the weight of water displaced by the instrument; then, as the specific gravity of water, or 1000, is to the specific gravity of the lightest fluid, of which you wish the instrument to ascertain the specific gravity, so is the weight of water displaced by the instrument to the weight of which the instrument ought to be made.

Having found this weight, unfix the scale and stem, and make the instrument, including the stem and scale, with the shots, about equal to this weight; then insert a piece of cork in the tube between the two bulbs, to keep the shots in the lower bulb, and fix the stem permanently and securely into the neck of the instrument; in order to which, make the cork fit very tight, and let it be rather longer than the neck: the part of the stem which is to be inserted in the cork should be warmed and rubbed with sealing-wax before it is inserted, and a little sealing-wax should be applied around the bottom of the cork where the stem comes through it, by which means the stem will be securely fixed in the cork after the latter is compressed by the neck of the instrument; when this is done, and the cork made to fit as tightly as may be to avoid the danger of breaking the neck, cut the cork level with the top of the neck, and cover it carefully and evenly with sealing-wax (which I find to be the best cement for the purpose), taking care there are no air-bubbles left in it.

The instrument is now made, ascertain its weight accurately, and call it as immerse it in distilled (or filtered rain water), of a given temperature (60 deg.), loading it with weights until it sinks to the middle of the stem; call the sum of

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a + b 1000

1001

1002.

So that, by finding and adding it to, or subtracting it from, the weight last found, a table inay easily be made, by referring to which the specific gravity of the fluid under trial may be ascertained immediately to the fourth place of figures; and by subjoining a table of differences it may be ascertained with very little calculation to the fifth and even the sixth place of figures; and, generally, as a + b: 1000 :: a + its load when sunk to the stem, the specific gravity of the fluid, the temperature being the same, say 60 degrees.

It will be found convenient to make one weight equal to b, or nearly so, and to use this, which may be called the water-load, with all fluids heavier than water, and calculate the table accordingly.

As this kind of hydrometer is not generally sold, nor the glass part to be had at the shops, I may observe that the latter will be best obtained from the Italian thermometer-makers. I have had mine blown for me by Mr. Pastorelli, of Cross-street, Hatton-garden, who charged me, if I recollect right, 1s. 6d. or 2s. for each; for the scale and stem fixed to it I have paid 18., so that the instrument, exclusive of the weights, will not cost more than 3s. The necessary weights are a set of grain and of pennyweights, and for cases in which great accuracy is wanted, a set for weighing decimals of grains, which last are best made of fine silver or plated wire.

This hydrometer combines the advautages of economy, accuracy, and of detecting a very minute variation in the specific gravity of fluids more than any other which I have met with. The last quality depends on the proportion between the bulk of the instrument and of the diameter of the steel stem; the one which I generally use is about seven and a half inches long, and weighs, with its water-load, 3071.2 grains. When immersed to the middle of the stem, the addition of 2 of a grain will produce a

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NECESSITY OF PROTECTING HUMBLE GENIUS.

sensible alteration, from which it is evident that the instrument will detect a variation of 1-20,000th part of the weight of the fluid.

This instrument requires much less liquor to use it than those with a long stem: the one above-mentioned requires nearly a wine quart, but it is larger than necessary. I have others so small as to be capable of being used with about half a piut, which will show the specific gravity to the 1-5000th or 1-6000th part.

The larger instrument will act with all fluids, from 800 to about 1250. If this range be insufficient, it may be increased by increasing the length of the tube which connects the two bulbs, and vice versa.

I will not detain your readers longer than just to observe that this instrument affords a very accurate balance, indicating to .l of a grain the weight of any thing weighing less than two or three

ounces troy.

I must add, that the efficiency of the instrument evidently depends on the cork being impervious to water, which I have found to be completely effected by the means I have described, as I have repeatedly ascertained, by keeping different instruments immersed for 24 hours and upwards.

NECESSITY OF PROTECTING

HUMBLE GENIUS.

The necessity of such an Institution as that which we announced the week before last, for the Assistance, Encouragement, and Protection of Native Genius," is strikingly exemplified in an able article on the subject which appears in this month's Number of the London Journal of Arts and Sciences." It details a most heartrending case of hardship and suffering, arising from the want of that aid which this Company is intended to supply. The unfortunate sufferer was James Cross, the inventor of a substitute for draw-boys,

which we have before noticed in our pages:

"At various times he had effected many important improvements in the weaving machinery used for figured fabrics, which, by his unwearied application, he at length brought to such perfection, as, with other great advantages, to render unnecessary the use of drawboys. During the progress of his labours, he was frequently encouraged by the manufacturers of Paisley, who saw and fully appreciated the value of his genius, with hopes of ample remuneration for

his persevering application. But when the inventions were pronounced complete, and more than his little means had been expended in arriving at this pefection, his only recompence was the high verbal approbation of his munificent and benevolent patrons; and that, too, after they had been entirely satisfied by actual experience of the great worth of the invention, and were daily reaping benefit from them. The Board of Trustees for the improvement of manufactures in Scotland awarded poor Cross a hundred guineas, which alone is a convincing argument in his favour; but this liberal gift was sunk in the perfection of his invention, and even then the poor victim was involved in debt. Unable to sustain such a pressure of accumulated misery, his health, previously injured by the privation he underwent to gather the means to prosecute his work, gave way to anguish and blighted hopes; and after more than twelve months lingering in expectation of at least a partial fulfilment of the brilliant prospects which had been held out to him, he died the broken-hearted sacrifice to avarice and base ingratitude, leaving a young, helpless, and motherless family, to inherit his PENURY and FAME. 'What man seeing this, And having human feeling, does not blush And hang his head, to think himself a man?'

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"Mr. Cross's numerous inventions form a grand era in the history of the art of weaving, and will be admired by posterity when the name and the woes of the humble author will have sunk togive a brief outline of them. So early as gether to oblivion; but we can here only

1804, he first commenced his observations upon the defects of the machinery then used for weaving, and almost every succeeding year his fertile genius produced some valuable improvement. In del of his machine for weaving harness1817-18, he niade the first working mowork without the aid of draw-boys, and submitted it to the inspection of a number of manufacturers and operative weavers, who unanimously spoke of it with the highest encomiums.

"This model being on rather a contracted scale, and necessarily imperfect, he was strongly recommended to construct one of larger and more serviceable dimensions, and was given to understand that his adviser would cheerfully pay every expense, whether or not his attempts were successful.

"Thus encouraged, he proceeded in his labours; but from many untoward circumstances, they this time proved unsatisfactory, after incurring an expense of 127. 15s. 6d. To defray this, as he had been promised, a subscription collected

ECONOMY OF FUEL IN HEATING STEAM-BOILERS, ETC.

amongst the manufacturers produced 121. 15s. 6d. leaving him a loser of 6., besides much valuable time. Notwithstanding these losses and frequent interruptions, from his very weak state of health, by persevering industry, during every moment's respite from disease, in 1820, he erected a larger machine. This he submitted to a Committee of mauufacturers and weavers, who very highly approved the principle, and warmly recommended a meeting, to "consider the propriety" of remunerating him.

A subscription, for the purpose of enabling him to prosecute his labours yet farther, was the consequence of this meeting, and the liberal amount of the collection was 167. 7s. 6d.-from which poor Cross had to pay for wages, &c. upwards of 127. With the residue he was to "proescute his labours," and maintain his family (then six in number, entirely dependent on him) for five months. Subsequently, being blessed with a short return of comparatively good health, and yet undismayed by the pitiful encouragement he received, he finished another machine of more extended and perfect operation. This also he laid before Committees of weavers and manufacturers. They were now so fully satisfied of his merits, that they this time gave written testimonials of their approbation (one signed by eighteen, and another by fifteen individuals); and a general meeting was called to reconsider the propriety of rewarding him, to which the public were invited by a cir cular letter widely distributed. At this meeting, a statement* of the poor sufferer's inventions was read, as also the flattering reports of the weavers and manufacturers, who had witnessed the ope rations of the completed machine; and the weavers were examined who then had it in actual practice. A subscription again succeeded this parade of mock gcnerosity, and produced the magnificent sum of 31. 1s. 6d. Such was the noble fulfilment of all the enticing prospects held out to him-all the generous promises, which induced him to sacrifice

"Extract from the Report of the Manufacturers, &c. being the statement alluded to:

Amongst the many improvements which Mr. Cross has made for the trade, may be mentioned-The Eyed Standard for Gauze Mountings; the Back Hiddles for Pressure Harnesses; the Barrel Machine aud Harness; the extending Tail for double Harness, for contracting the Flowers, which, in many cases, saves nearly one-half the expense of flowerlashing, the pressing treddles not being required as formerly,

These have all been proved to be of

great use.'

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time and health, which might, and would otherwise have been employed advantageously for himself and family.

In making the numerous experiments necessary to enable him to bring the invention to perfection, he expended and contracted debts exceeding 1007., exclusively of the maintenance of his family during the long period that he was so engaged; and for this, the whole recompence he received from the manufacturers amounted, as we have shown, to 31. 14s. 6d.! He now became but too fully sensible how miserably he had been deluded; and oppressed by all the horrors of debts, which he saw no possibility of repaying-harassed by continual anxiety, both of body and mind, and the bitter conviction of his utter destitution, his energies gave way beneath the accumulated mass of woe, his enfeebled body became the prey of sickness, and he sunk into a state of entire helplessness. Thus he lingered, the miserable victim of his own powerful genius, till March, 1824, when, at the early age of 45, he was happily released from further earthly trouble. Previously to his death, he had the satisfaction of seeing his machine generally adopted by the liberal manufacturers, and several gave written testimony of the great benefit they derived from it. The noble donation of the Board of Trustees came to cheer his iatter days also, but it was too late to renovate his worn-out frame. But for the real benevolence of one individual, his four orphans (three girls and a boy, the last but six years old) must have become entirely destitute, and have suffered the very extreme of want. By his humane aid, however, and the employment of the eldest girl as a servant in one of the manufactories, as far as the calls of nature go, they are perhaps as well provided for as many of their neighbours in the same class; but not one of them has yet received any education whatever, and unless benevolence again exert itself, there seems no possibility of their ever obtaining it.

"Such has been the melancholy fate of one individual, and this one instance, it is hoped, will be thought a sufficiently convincing demonstration of the urgent and crying necessity, for the adoption of instant and energetic measures for obtaing a permanent barrier to its recur

rence.'

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ECONOMY OF FUEL IN HEATING

STEAM BOILERS, ETC.

SIR, I wish to call the attention be derived, as regards the consumpof your readers to the advantage to tion of fuel, by making the flues which surround the boiler much nar

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CLEARING BEER WASHING MACHINE-PROFIT AND DISCOUNT.

rower than is usual. The common
width is, I believe, nine inches, in-
stead of which I would recommend
them to be made not more than four,
or four and a half inches wide. I
think I am justified by my own ex-
perience, as well as by that of a
friend of mine, who has also made
the trial, in asserting that the saving
in fuel, by the above alteration, will
not be less than one-third of the
whole. I have known it estimated
at one-half, where it has been tried.
I hope some of your readers will
make trial of the plan, and commu-
nicate the result in your valuable
work; and if, as I anticipate, it
should be found to answer and be-
come general, it certainly will be
such an important saving as may
fairly be reckoned a national advan-
tage. I imagine that the principal
reason for making boiler flues so
wide as they are usually made, is,
that a boy may be admitted into them,
for the purpose of cleaning them,
which purpose was, in the cases above-
mentioned, accomplished easily and
effectually, by removing a stone or
brick at each end of every fluid, and
passing a brush with a long handle
along them this method will have
the recommendation, to every friend
of humanity, of superseding the ne-
cessity of climbing-boys in the in-
stance alluded to. It will be seen
that the plan is only adapted for
those flues which are straight, or
nearly so; but there are few which
are not so. One disadvantage of the
plan is, that the flues will require
cleaning more frequently than when
made on the present plan; but this
is, I conceive, of no importance,
compared to the advantage in the
saving of fuel.

I remain, Sir,
Yours respectfully,

J. S. M.

MR. DICKENSON'S APPARATUS FOR

CLEARING BEER.

SIR, I observe, in Number 81 of your Mechanics' Magazine, page 390, au invention made by Mr. Dickenson, upon a plan, which certainly is a very good one, for clearing Beer, after being fermented

in the gyle-tun; but if it is intended to supersede the use of the gyle-tun, I wish Mr. D. would communicate, through the medium of your valuable publication, his method of keeping down the temperature, which I think would be so high, from fermenting in a close vessel, as to injure and impoverish the beer.

Mr. D. would oblige if he would state the increase of temperature of each day during the fermenting process.

Yours respectfully,
Leeds, April 12th, 1825.

WASHING MACHINE.

XX.

[MECHANICS' Mag., page 424, VOL. III.] (Explanations requested.)

SIR-Any hint to improve so important a business as Domestic Washing, is of too much value to be suffered to pass away for want of some little explanation-I allude to the short letter of your

Correspondent, R. Burton, inserted in
Number 83. I wish your Correspond-
ent had been a little more explicit, and
told us how the board is used particu-
larly-whether it is placed in the bottom
of the tub, or diagonally-whether the
flutes are placed horizontally or perpen-
dicularly-and whether the pressure is
above or under water. It may be said,
perhaps, that all this might be found out
by experience; but I should like to try
the way which your Correspondent says
has been much approved of by very com-
petent judges. Besides, my servants are
very stupid, and would never find out
any thing by their experience; indeed,
we are thankful if they understand and
do what is pointed out to them. Per-
haps R. Burton may uot think it too
much trouble to write you a few lines
more on the subject-it will oblige
Your constant Reader,
March 31st.

ISLINGTON.

PROFIT AND DISCOUNT. SIR," An Old Manufacturer" will find, on a review of his observations respecting Profit and Discount, that he has indeed amused" himself, but by no means instructed his readers; and, to convince him of the fallacy of his reasoning, we will proceed to an investigation of the example proposed by M. W.

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Suppose an article cost 50%., on which it is wished to make 7 per cent. profit, what must the selling price be, so as to be able to allow 3 per cent. discount?" No one will dispute, that if the selling price were 537. 15s., 7 per cent, would be the sum gained: but as a further discount of 3 per cent. is to be allowed, besides the clear profit of 7 per cent.,

this

WATCH KEYS-NEW PATENTS.

is only a first step towards accomplishing
the object. Continue the operation by
adding to.....

3 per cent, on 53 15 0
Ditto

1 12 3

Ditto 0 0 11

53 15.0 1 12 3

0 0 11

0 0 0

which together will make... £53 8 23 It appears this must be the gross selling price to allow 3 per cent. discount, and secure 7 per cent, profit. As a proof, the following will satisfy, no doubt, the most sceptical:

From gross selling price... 55 8 2 Deduct 3 per cent. discount 1 13 2

£53 15 Deduct cost price........ 50 0 Leaving.

0

0

3 15 0

or 7 per cent. on money advanced. The block against which "An Old Man" has stumbled, is in having calculated the percentage on the selling price of the goods, instead of on the capital employed. A slight view of the rules in any book on "Plain" Arithmetic, under the head of Profit and Loss, will set him right on this subject. That my supposition on this head is well founded, is evident from his assertion of gaining only 20 per cent, in selling goods for 1007. which cost 207., and it must appear clearly to any one that the profit would be 25 per cent.

Again, he is equally unfortunate in his next proposition," to gain 20 per cent, and allow 10 per cent. discount.' He says, "let the prime cost be 727"-the result of his labour is 1007. Now, the gross selling price, in this instance, need not be a penny more than 967. Gross selling price........96 0 0 Deduct 10 per cent. 9 12 0

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but for the convenience of wearing. The old shape was so crooked as to be inconveniently liable to catch ladies' gowns in dancing, or when at any time assisting them; and by the entanglement, in very many mechanical operations, it caused the watch to be jerked entirely out of the fob, more particularly before braces or suspenders were used, which was

about the same time that the form of the watch keys was changed. In riding, especially in leaning forward to open a gate, the key, from its many angular shapes (somewhat as crooked as the Isle of Man arms), often got fixed under the pommel of the saddle, and on rising, the watch was drawn out suddenly, or the chain broke.

The present form is doubtless the most covenient for wearing, though certainly not for winding; but as the wearing is for twelve hours or more, and the winding for less than half a minute, custom has naturally, in my opinion, given rise to the present shape, notwithstanding the truth of Senex's observation as to the winding up.

vented to remedy the inconveniences A triple-jointed steel key was inof both the above-mentioned, which, when suspended and at liberty, was in a vertical posture, but on application it was of the old shape. Gold or copper,however, is not strong enough for joints so small, and a steel key does not harmonize well with gold seals and chains, or even gilt ones; though this kind is now much in use with the lower classes in the country, particularly ploughmen and carters, mostly accompanying a steel chain. The least satisfaction to any of your Correspondents will be a pleasure to

AGRICOLA.

NEW PATENTS.

Chevalier Joseph de Mettemberg, Foleyplace, Mary-la-bonne, physician; for a vegetable mercurial and spirituous prepa and also a particular method of employration called Quintessence Aulepsiroque, ing the same by absorption as a specific and cosmetic.-Feb. 26.

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