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rence only extended to the height singular proofs of strong and activo of thirty-three feet. When Dr. magnetism. It contained a reBirkbeck told this story, there markable quantity of steel, and was a general laugh among the every part of it exhibited vigorous artisans present, which showed polarity. Every screw displayed that they comprehended all the its influence, and the frame alone absurdity of the philosopher's an, contained ten large and several swer. Thus, then, we see, and small screws; and the same inthe sight is most cheering, that tense and active magnetic power the workmen of the British metro. was exhibited by the chain, the polis are more correct in their axles of the wheels and pinions, knowledge, and possess pro- the arbor of the fusee, and the bafounder ideas than the Floren- lance of its springs. Mr. Cox, the tine Sage, even in his own favour agent for Arnold's chronometer at ite pursuit; and to Galileo cannot Plymouth, remarked, when he saw be denied the praise of having been this chronometer, that it appeared one of the most profound men, and nothing less than a magazine of magone of the greatest discoverers of nets. Mr. Scoresby recommends his age.

platina, or an alloy of platina, for

the balance of chronometers. Gold NATIVE GOLD. MURIATIC is said to be considered as well

AND SULPHURIC ACID IN adapted for the balance-spring.

A RIVER. M. HUMBOLDT bas informed the TO CORRESPONDENTS, Academy of Sciences at Paris, W. L**y's communication has been that he has received information received, and will appear in our next. from Messrs. Boussingault and Gas will see that his suggestion had Rivero, two enterprising travellers occurred to ourselves. There are so in South America, of a large mass of many persons about town who supply native gold having been lately found chemical instruments, that it would be near Antioguia, in the Republic of invidious in us to recommend any one. Colombia, weighing eight arrobus, We may say, however, that Mr. Guror above 190lbs. The same gen- ney's blow-pipe is chiefly made by Mr. tlemen have detected sulphuric and Banks, mathematical instrument-maker, muriatic acid in the waters of a Strand ; that if Gas live east of Temlittle river, which falls from a vol- ple-bar, he may seek the shop of Messrs. cano, called Puracé, near Popayan, R. and G. Knight, Foster-lane, Cheapand which is pamed by the inha- side; if on the west side, he may embitants Vinegar River. They also ploy the scientific Mr. Newman, of say schools for instructing miners Lisle-street, or Mr. Elliott, 21, Great are about to be established in tbat, Newport-street. country; and already there are We defy the threats of Azot; and lithographic and other establish- are not, as he will find, so easily stifled. ments, which show it to be in an Some of our Correspondents comimproving state.

plain of our being too learned. Is this

our fault, or theirs? We will readily MAGNETIC INTENSITY. insert, if good, their unlearned Essays. Mr. G. HARVEY, M.G.S. &c., has Cheap Drunkenness, which has come found, by Coulombe's apparatus, to hand, will appear in our next. that a box chronometer exhibited Anti-Stahl is unavoidably postponed,

** Communications (post paid) to be addressed to the Editor, at the

Publishers'.

London: Published by JOHN KNIGHT and HENRY LACEY,

24, Paternoster Row.

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CONTENTS. Mr. Gurney's Instrument for collect-- Chemistry as a Science. Art. IX.

ing the Products of Decomposi. Boron. Sulphur .............. 140

tion effected by the Blow-pipe... 129 Ant-hills in Norway .............. Bread .......................... 131 Temperature at we

1 Oil emits an Cheap Drunken

inflammable Gas .............. 143 Tannin in Chesnut-tree Bark...... 135 Lithography .................... Hydrogen Gas Lamps ............

136 Test for Gum .......... To make Chalybeate Water........ ib. Combustion of Iron in Vapour of Effects of Atmospheric Pressure on Sulphur .....:

the Rates of Chronometers ...... ib. Vinegar manufactured from Ants .. 144 Self-acting perpetual Blow-pipe.... 137 The Quarterly Journal of Science Analysis of Scientific Journals. An versus Mr. Ivory................ ib.

nals of Philosophy for May 1824 ib.

MR. GURNEY's INSTRUMENT elements of the substance you are

FOR COLLECTING THE about to examine, and are only PRODUCTS OF DECOM- enabled to judge of the nature of POSITION EFFECTED BY the mineral, or other body thus THE BLOW-PIPE.

acted on, by certain appearances In our last Number we gave a which take place during the immedrawing and a description of Mr. diate time of the operation : this Gurney's blow-pipe. But by this also happens in using the common mode of operation you lose the blow-pipe, when propelling the ame of a lamp, at least, when tinued. The glass may be removed those substances are operated on by placing the slab under water, which it is capable of subliming. either with the safety cylinder and To remedy this obvious inconve- flexible tube attached, or by prenience in mineralogical research, viously unscrewing it from the and to enable the operator to pre- tablet, without any possible loss of serve all the elements of any solid the contents, and may be decanted substance he wishes to examine in into smaller vessels for more acchemical analysis, when they are curate examination. Any solid thus separated from their original substance, whether a mineral or state by this powerful agent, I chemical body, may be analysed have contrived, says Mr. Gurney, in the same way, and the most saa simple apparatus, Fig. 1, and tisfactory results obtained which I find from experiment to Should the water, formed by the answer the purpose intended. a combustion of the oxygen or hyis a solid slab of plaster of Paris drogen gases, be an objection to or of metal, with its upper surface the immediate object under analyground perfectly true, so that, sis, a mixture of chlorine and hywhen a ground glass is placed on drogen in the proportions to form it, it may remain air tight on the muriatic acid may be used to proedges, similar to that on the table duce the flame from the instruof an air-pump. In the centre of ment. the surface of this plate is a little Fig. 2 in the drawing is illustrafurnace, b, into which one of the tive of some curious phenomena jets belonging to the instrument is concerning flame, which Mr. Gurmade to terminate, by perforat, ney observed during his experiing from the side through the ments with the blow-pipe He nosolid part of the slab. Over ticed in his attempts to distinguish the furnace is fitted a ground flame by pressure, that its colour bell glass, or part of a large tube, changed to all the tints of the rainwith a cap and stop-cock affixed, c, bow; and by giving certain deand the whole made completely grees of pressure, he was able to air tight. To the stop-cock is at produce any colour at pleasure, tached a bladder or silk bag, g, in the tints following each other in the usual manner.

the same order in which they are The method of using this ap- observed in the prismatic specpendage in connexion with the trum. On pursuing the inquiry blow-pipe is this : the substance which this suggested, he found that to be examined is placed into the each of the rays had a different heatlittle furnace; the jet which per- ing power, as in the prismatic specforates the slab is screwed to the trum; and that, as in it, there was safety apparatus of the instru- a point beyond the rays of colour, ment; and after the pressure has where the heat was greater than in been on the press-board, either by any part of them. On applying weight or the hand, the gas is to sufficient pressure to extinguish be inflamed at the jet by a taper, the flame, the wire, with which he and the glass instantly inverted was testing its power, instead of over the furnace; the intense heat becoming, as he expected, cold, of the blow-pipe will now fall on became more intensely heated, and the mineral, and the whole of the fused into globules. At this time volatile or gaseous parts will rise, there was not a vestige of flame. and either be condensed on the Mr. Gurney afterwards found, by inside of the glass, or pass into the holding a bar of platina in a flame bladder through the upper stop- produced by the blow-pipe, it incock in the gaseous form; thus the creased in its temperature as it whole of the elements will be re- approached nearer the jet. From tained, and may be examined by this, he says, he is convinced that the proper tests after the action of flame is hollow, and consists of a the instrument has been discon- thin film, or coat of ignited matter. This coat is composed of several been instituted as a matter of polayers or coats, lying one on the lice, to ascertain what quantity of other: the outer coat is white, weight bread lost in the baking, then comes red, then orange, yellow, are, in some respects, very correct, green, blue, violet; and within the they are essentially incomplete as violet is an invisible coat where to the changes which the flour unthe combustible matter is con- dergoes before it becomes bread. densed, where the chemical change We are obliged, therefore, to begin between the elements takes place, this part of our Article by acknow.. and where alone the heat produced ledging that, on this subject, our by the combustion is evolved or information is neither so complete formed. This is fanciful enough: nor so accurate as we could dehowever, it is ingenious; and Fig. 2 sire it. is a copy of Mr. Gurney's diagram Bread, as our readers know, is for illustrating it. a is the com- made from flour, and more genebustible gases mixed before con- rally from wheaten flour than from densation; b the line or invisible - any other. This is found to concoat of actual union, or where the sist, chemically, of a small portion combustible matter is condensed; of mucilaginous saccharine matc the first effect of heat in producing ter, solable in cold water, from colour, or the violet layer; d the which it may be separated by evagreen; e the yellow ; f the orange; poration; of a great quantity of g the red; h the full combination starch, which is scarcely soluble of rays, or white, gradually losing in cold water, but capable of comthemselves in the atmosphere. We bining with that fluid by means of shall not follow Mr. Gurney fur- heat; and of an adhesive grey suba ther in bis speculations ; but to us stance, called gluten, insoluble in they appear more imaginative than water, ardent spirit, oil, or ether, correct.

and which, in many of its proper.

ities, resembles an animal subBREAD.

stance. The problem is; to ascer... (Continued from p. 102.) tain wbat changes these substances It is the remark of a very intel- undergo. When the flour is kneadligent chemist, that no set of ex- ed with water, it forms a tough inperiments, with which he is ac- digestible paste, in which all these quainted, have been instituted and constituent substances may still be carried into effect for ascertaining found. Heat produces a considerwhat happens in the preparation able change in the glutinous part of bread. As the change which of this compound, and renders it the flour undergoes is, in all re- easier to chew and digest. The spects, a chemical change, this cake is, however, in this state fact, which is correctly stated, is heavy and tough, and is only made very surprising. Notwithstanding light by the addition of leaven, or this, we remember, that the early some substance having correspond. editions of a very celebrated system ing properties, or capable of proof chemistry contained a detailed, ducing similar effects. If flour be if not a correct description of the mixed with a small quantity of whole process. We observe, that water, and kept in a warm place, it has been omitted in later editions, it undergoes a species of fermenta which is a tacit proof that it was ation; it swells, becomes spongy, unworthy of public notice, and of and at length acquires a sour taste, the author's reputation. The prin- and gives out a sour smell. This cipal experiments on bread with is leaven. If this is left to itself, which we are acquainted, were it at length begins to putrefy; minmade in France, a circumstance gled with other dough, it niakes it not surprising; for though other rise readily, and gives it a greater countries are called the land of degree of tenacity; the dough or cakes, that is the land of bread. paste undergoes spontaneous de Though these experiments, having composition, the saccharine part is :

converted into an ardent spirit, places, however, such as on board the mucilage tends to acidity and ship, and in warm climates, where . mouldiness, and the gluten verges no beer is made, leaven is still getowards putridity. During this perally in use. Yeast is found to process a considerable quantity of make the dough rise more rapidly gas is produced, which is supposed than leaven, and therefore makes to be carbonic acid gas ; the dough the bread lighter. becomes porous and increases its It is obvious, that making bread bulk. If this process be suffered is a most delicate operation, reto go on by itself, the outside and quiring definite proportions of wathe inside are not equally affected; ter, flour, and yeast, or leaven; - and it is found that some parts be- the dough, also, biust be kept at a come mouldy before the others have certain temperature, or, if too hot, acquired the proper degree of fer- the fermentation goes on too ra. inentation. It is found by expe- pidly, and if too cold, will not go frience, that the addition of a small on at all: the oven, too, must be

quantity of leaven, and the em- of one certain temperature, or it ployment of a gentle heat, accès would not properly bake the bread. -Jerate the process of fermenta. It is also to be observed, that dif

tion, which kneading makes equal ferent kinds of four require differ-througbout; and a sufficient quan- ent quantities of water, and do not

tity of carbonic acid gas is gene- all ferment alike. To regulate all -rated from the saccharine matter, these nice points, the baker has no

to make the bread light before the instruments, and nothing but his gluten has begun to putrefy. The experience to guide him. He - tenacity of the gluten prevents the trusts to his sensations : throws a s, escape of the gas, and the bread little flour in his oven, and observes

becomes light and porous. A cer- if it blackens or burns; plunges his ,tain quantity of moisture is neces- hand into the water, or feels the --sary for the continuation of this dough; and so nice does his tact - process; and baking the bread, become, that what no philosopher

whatever other effect it may have, could, perhaps, tell by the most ac- for this point is not exactly ascer- curate of his instruments, the jour- tained, evaporates the moisture neyman baker, or the housewife, so as to check the fermentation, decides at once; and, perhaps, of though, unless carried to a very con- all the batches of bread baked in siderable excess, it does not wholly this metropolis, not one out of ten stop it. The very grateful smell thousand is spoiled. It must not, of new baked bread, and the therefore, be supposed, that instruconstant alteration which takesments are of no use: thermomeplace in it as it grows stale, ters, to measure the heat of the losing this smell, changing its bakehouse, and pyrometers, to taste, and becoming hard and measure the heat of ovens, have dry till it moulds, are all proofs been employed with advantage. of a chemical change constantly No instruments, however, can supgoing on in bread, though of what ply the want of skill and practice; nature has not been distinctly and, where these are, instruments ascertained. Very great care is such as we have mentioned may be necessary in making bread of lea- dispensed with. ven; and, in general such bread The method of making housedoes not get properly fermented, or hold bread is said to be this :-To it acquires an acid taste, from hav- a peck of flour they add a handful ing too much feaven mingled with of salt, a pint of yeast, and three it, or from the fermentation being quartz of water. The whole being allowed to proceed too far; and it kneaded in a bowl or trough, will having been found that yeast an- rise in about an hour; it is afterswers all the purposes of leaven, wards moulded into loaves, and it is very generally employed in put into the oven. To make French most parts of Europe. In some bread, . ten eggs, a pound, and a

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