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been made ill, to point out a test for copper in sweetmeats; and we are now called on by the following statement to point out a test for lead in lolly pops:—" One pennyworth of red balls, called, we believe, Nelson, or Waterloo Balls,— there were no such line names in our lick-finger days,—yielded on analysis 30 grains of an indissoluble matter resembling red-lead, which on being fused with the blow-pipe produced 24 grains of lead in a metallic state. We wish," says the author of this notice, which is taken from the Stockport Advtrtiser, " to impress upon the minds of parents the necessity of strictly charging those to whom they occasionally entrust the care of their children, not to purchase for them sweetmeats of this description, since it cannot be doubted that the use of these deleterious compounds has in many instances produced injurious effects oh the system, which nothing could ever eradicate." There is, in fact, no other way of escaping poison but not to eat; and we join the Editor qf the Stockport Advertiser in cautioning parents not to suffer th»ir children to be unnecessarily poisoned. They must not eat sweetmeats; but as it is to be apprehended they will, in spite of our caution, we shall perhaps do them some service by putting them in the way of ascertaining if their sugarplums contain poison, and by suggesting to those who use lead for colouring them the use of a 'substance which will answer the same purpose without being quite so virulent a poison.

We have already described— (see p. 227,)—the mode' of producing sulphuretted hydrogen gas; let this I - combined with water in 'the following manner:—In the first ••place, it must be received in a bottle placed over the pneumatic ;ti*ough, or a common basin, as described in p. 9, No. I. of the Chemist. After the gas has been thus collected, cork the bottle while its month remains under water, and remove it, and then place it inaverted in a cup containing dis

tilled water; in a few hoars, the water will have ascended considerably up the bottle, and this water will be impregnated with sulphuretted hydrogen gas. In water thus impregnated, and slightly acidulated with muriatic acid, put the colouring matter of the sweetmeats, when, if it contains lead, the impregnated water will shortly assume a dark brown or black colour. The impregnated water should not be made very long before it is used, as the hydro°-en will quit the sulphur, which is then precipitated in the form of a white powder.

A very fine red may be made of cochineal, as recommended in various cookery books, for the colouring of jellies; but as this may be too expensive, and as children are not particular as to shades we recommend pastrycooks to slice beet-root very thin, to boil and strain it, and use the liquid, which will give a deep red colour to their sweetmeats. In fact, there are so many comparatively harmless and cheap modes of colouring paste of every description, that not only are we surprised any body should give himself the trouble and go to th« expense of poisoning children, but we know not which of these numerous methods most to recommend. There is no excuse, however, for using lead; and most certainly lie who puts it into his plums deserves not to be dealt with.

ANSWER TO QUERIES.

To the Editor of the Chemist. Sir,—In reply to the Query of your Correspondent H. S., inserted in No. XIV. of your valuable publication, "The Chemist," I beg to suggest the following method of making a durable ink, which writes pale, but becomes black on drying

J.E.K.

Mix together in a quart wine measure of spring water, cold^

2 oz. of Aleppo galls, bruised,

1 oz. of green copperas,

1 oz. of gum arabic, And shake tliem twice a day for ten days, when it will be fttfp;r,us0.

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CHEMICAL APPARATUS.

CALORIMETER.

Our plate represents an instrument contrived by the two celebrated Frenchmen, La Place and Lavoisier, to determine the specific beat of bodies. It is called a calorimeter, or measurer of heat, but is neither a very correct instrument, nor of great utility. Some very interesting experiments were, however, made with it, and some curious conclusions drawn from them, by these two celebrated Frenchmen, at a time when the theory of heat was very imperfect, and much studied; which make us think we shall do our readers no disservice by giving them a representation of the instrument. It was constructed tin the fact, that the heat of a hot body surrounded by ice does not pass through the ice, but is all employed to melt it; and as Dr. Black and others had previously ascertained, that a certain quantity of heat was necessary to convert ice into water, the quantity of ice melted by the heat of the inWbsed body, it was concluded, Would be the measure of tho quan

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tity of heat which escaped from it, and in this manner that the relative specific heat of all bodies thus examined might be ascertained. The calorimeter consists of three vessels, inclosed one within the other; the innermost of which, 4, to contain the substance submitted to experiment, is a cage made of iron wire, covered by a lid of the same materials. The middle vessel, or cavity, contains the ice, which has under it a sieve, or grating, mm. As the ice is melted, it runs through this and through a conical funnel into a receiver placed below. The external vessel, a a, is also filled with ice, to prevent the effect of the air and other surrounding bodies. The water produced from it is carried off by another pipe, S T, so as not to mix with the water from the first. When the machine is to be used, the outer and middle vessels are closely tilled with pounded ice, and the substance submitted to experiment is placed in the inner vessel, and instantly covered. When the body has cooled down to the freezing point, the water is carefully weighed, and is supposed, taking it for granted tbat a certain quantity of heat has been necessary to form each drop, to measure the quantity of beat which has escaped from the body to bring it to the freezing point of water. On the late Mr. Wedgewood attempting, however, to repeat the experiments of the French chemists, the water which raft from the ice froze again; and as it does not seem possible to obviate this, at least not without exposing the water to heat from some other source, the calorimeter is, as we said before, neither an accurate nor a convenient instrument. The freezing is occasioned by the evaporation of the water, and as it has been shown that this is always greatest at the temperature of 32°, which is about the temperature of the water, a very slight diminution of temperature by evaporation will cause the melted ice again to freeze.

MONUMENT TO MR. WATT.

The public Meeting on Friday, June 18, to open.a Subscription for the purpose of erecting a Monument to the late James Watt, promises to have so muchinfluence on the future prosperity and character of the community, that, although it is not our business to keep a record of public events, we can by no means pass by this one in total silence. The Meeting, as our readers are most probably aware, was called by some of the first men of the land, and was attended by many noblemen, men of science, and men of business, among whom were the following distinguished individuals:—The Earl of Liverpool, First Lord of the Treasury; the Earl of Aberdeen, lately his Majesty's Ambassador at Vienna; Mr. Peel, Secretary of Stute for the Home Department; the Hon. Mr. F. Robinson, Chancellor of the Exchequer; Lord Bexley, formerly Mr. Vansittart, and Chancellor of the Exchequer; Mr. Huskisson, President of the Board of Trade; Sir J. Mackintosh, one of the leaders of the Opposition; Mr. Brougham, another of these leaders; Admiral Sir Isaac Collin; Mr.

Wilberforce, M.P.; Sir Humphrey Davy, President of the Royal Society; Mr. Bolton, son of Mr. Watt's late partner; Mr.Wedgewood, theporcelain manufacturer; Mr. Turner, a great canvass manufacturer; Dr.Birkbeck, the President of the Mechanics' Institution, ScC.&c. Of course the resolutions were unanimously adopted; and the sum of sixteen hundred pounds, of which, his Majesty gave live hundred, was immediately subscribed. The work thus happily begun will, no- doubt, be successfully completed; alld ere long a monument to James Watt will be placed in one of our national temples, as a memorial of his stupendous genius, and of our gratitude to that Power which made him the instrument of bestowing almost immeasurable benefits on the whole human race.

Mr. Watt was not only a mechanic, he was also a chemist; and we are proud of the opportunity to hold up the honours bestowed on him, as an enoouragement to our youthful readers. As was happily explained at the Meeting by Sir Humphrey Davy, Mr.Watt's "discoveries were not owing to chance,, but were founded on delicate and refined experiments connected with the discoveries, as to heat, of Dr. Black. He was equally distinguished (he said) as a natural philosopher and a chemist;" and his first important discoveries were made, in chemistry; and his first important invention was an application of chemical principles to steam-engines. His great mechanical improvements iu them only began at a later period. In 1769, he took out a patent for lessening the consumption of fuel in steamengines; and it was not till 1780 that he found the method of applying the movement of the pistons in straight lines to wheels and mill work. We have already, iuour account of Bleaching, mentioned Mr. Watt asoneof the great improvers of that process, and as having been instrumental in applying the use of chlorine to bleaching on a large scale. In fact, his peculiar merit appears to have consisted in a

steady application of the discoveries of science to the purposes of life. He was not bred A pliiloso*

Eher but a man of business, having is way to make in the world; and it deserves to be remarked, that the guiding motive for his exertions was a clear view of his own interest. It was his pride to make useful discoveries; and all his inventions tend to improve or adorn life. His character as a man was fully equal to his reputation as a mechanist and a chemist. Both the Earl of Liverpool and Mr. Brougham bore testimony to his private worth. The latter said, nothing " could be more pure, more candid, or more scrupulously loving of justice than Mr. Watt." He was distinguished, too, by a total want of jealousy of other scientific men, and by the greatest amiability to all his friends and relations. In short, he was admired in the world for his genius, and loved in his family for his virtues. His kindness, his benevolence, and his humanity spread a lustre over his mechanical and chemical pursuits; and the vast influence of his inventions made his amiable qualities more lovely. His Character Was one of the most splendid examples we know of a union of gentleness and strength; Of the greatest moral beauty combined with the highest degree of intellectual power.

Certainly, therefore, no other individual could have been selected more deserving national honours, and from honouring whom more permanent benefit will accrue. At any period, and done in any manner, this circumstance would have had most beneficial effects; but now, when there exists such a facility of making all public events known that the whole people of this empire, like the inhabitants of the ancient Greek republics, live, as it were. Within hearing of one another, and when the manner of adopting these resolutions was so public and dignified, the results will be doubly beneficial. Mr. Watt was not a warrior, over whose victories a nation may mourn, doubt

ful whether they have Added to its security, and certain they have diminished enjoyment and abridged freedom. His were the conquests of inind over matter; they cost no tears, shed no blood, desolated no lands, made no widows nor orphans, but merely multiplied conveniences, abridged our toils, and added to our comforts and our power. The good policy of erecting monuments to mere warriors, Who combat at other men's bidding, careless of right, and only greedy of honours and emoluments» who enforce the observance of a creed and defend freedom of worship with the same zeal, and who are as ready to support oppression as defend liberty, which has hitherto only been a matter of doubt in philosophic minds, will become* by the example of this Meetings the general sentiment. Henceforth men will perceive the folly of encouraging the shedding of human blood; will recognise the wisdom of uniting glory with usefulness { and will only erect-monuments to those in whose labours there is nd alloy of misery and mischief. It is the consecration of this sentiment, by the presence of the statesmen of all parties; who unfortunately have in general only taken the lead when restrictions were to be imi posed, industry depressed, or wars encouraged, that makes us look on the public Meeting to erect a monument to Mr. Watt as an event which, in its result, will be one of the most remarkable of the present period. In fact, for men to provide for their own interest and their own comfort seems so natural, as to need no encouragement. Statesmen therefore have not, in geneYal, bestowed any marks of approbation on those who have most successfully cultivated this part of all men's business. The present, we believe, is the first instance where they have thought it necessary to confer honours on a man who was fortunate enough, in the avowed pursuit of his own prosperity, to add to the happiness and greatness of his country. We have before said, that the guiding motive of Mr. Watt, in all bis applications of the principles of science to the purposes of life, was a clear view «f his own interest. He is distinguished from other public benefactors, by never having made, or pretended to make it his object, to benefit the public. He was not a political quack, or a religious charlatan, who pretends to live and act only for others, but a man occupied with the care of his own fortune; and we have the united testimony of all the great and distinguished persons who were present at the Meeting, that this unpretending man in reality conferred more benefit on the world than all those who for centuries have made it their especial business to look after the public welfare. It is the holding up such a man, actuated by such motives, to the admiration of the public, that we regard as the circumstance most peculiar in this case; and we should be wanting in our duty to our youthful readers, if we did not press this on their attention, and caution them against supposing, because Mr. Watt has obtained public honours for pub'ic services, that the object of their exertions should be the benefit of that public. It is plain that the faculties of every man are only calculated to promote his own happiness; and the example of Mr. Watt shows that he is the best citizen who pays the closest attention to his own interest. It sets in a clear point of view the principle which has often been theoretically, but not effectually urged, that the only means of promoting general good, is for each individual, as nature dictates, to attend to himself. Honouring the man who has done this, argues a sane mind in the public; and the proceeding having received the sanction of our rulers, the opinion will become fashionable. It is the first severe and effectual blow which has ever been given by authority, to all those moral quacks who, with/ sense and intellect no more expanded than other individuals, assume something like the character of divinity, claim a

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TO MAKE A SOLID OUT OF TWO INVISIBLE GASES.

To the Editor of the Chemist.

Sir,—You showed your readers, in No. XII., how to perform this experiment; but there is another method of performing it, which is easier, and quite as amusing. It is as follows: — Take two widemouthed decanters, as represented in the subjoined sketch; pour a very small quantity of muriatic acid in one, and liquid ammonia into the other, just sufficient, when rinced round, to moisten every part of the inside of the glasses. If these decanters be kept at a distance from each other, they will appear empty; but invert one. within the other, as seen in the plate, and they will both be filled with dense white vapours, like, clouds, and at length a crystallized crust will be formed on the inside of the glasses, which is muriate of ammonia.

I am, Sir,
Your obedient servant^ ,,

SlMPMCITAS.

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