to them, and describing these terms as the tools with which he worked. He then proceeded to explain that all the changes which take place in the objects about us, that are unaccompanied by sensible motion, were the results of the union or separation of two or more substances, which he characterized as unalterable elements. The objects of Chemistry he explained to be an inquiry into the constituent elements of bodies, and to ascertain the laws of chemical changes. Of some substances the different natural properties (meaning the commonly observed properties, we presume) are found to be a correct index to their different chemical properties; of others the reverse is the case. Thus charcoal or carbon differs as much in appearance as in its chemical properties from potash; but it differs still more in appearance from the diamond, though its chemical properties are found to be very nearly or precisely the same. To ascertain chemical properties, two modes are had recourse to. Or chemical researches are carried on both by analysis and synthesis. Thus by applying either heat or a strong acid to marble, which, in the language of chemistry, is carbonate of lime, it is separated into the two substances, lime, and carbonic acid, each having very different properties from the marble. This is the analytical mode of investigation. If the carbonic acid gas, disengaged from a piece of marble, is conveyed into a solution of lime, the carbonic acid gas unites with the lime, and again forms a substance, having the chemical, but not exactly the mechanical properties of lime. This is the synthetical mode of examination; and when the two modes exactly correspond, chemical research is complete and correct. The professor disengaged the carbonic acid gas from a piece of marble, by the action of muriatic acid, and he conveyed this same gas into a solution of lime-water, and there re-formed a carbonate, illustrating his doctrine by a very appropriate and beautiful experi

ment. There are only a few cases, however, in which the Chemists' art can reproduce the substances he has destroyed. Of these few, water furnishes one of the most striking examples. By analysis it is separated into oxygen and hydrogen, and by synthesis this oxygen and hydrogen are again formed into water, The Chemist can, in many cases, reproduce bodies with the same chemical, which have not, however, the same mechanical properties. All the bodies of nature, of whatever description, are composed of two or more of the elementary substances; those only being called elementary substances which the Chemists' art has not decomposed; and this art frequently proves that the substances which are called elements by one generation of Chemists, are by the next shown to be compounds. Thus only a few years ago lime was regarded as a simple substance; but the experiments of Sir Humphrey Davy showed that it was a compound of metal, which he called calcium and oxygen. Having thus shown to his audience the two modes of chemical investigation, and explained what was meant by a simple or elementary substance, and enumerated those at present known, the Professor proceeded to sketch the outline of the course he was to deliver. We were not so fortunate as to comprehend exactly either the principles or the details of his arrangements; but we understood him to say, he should first explain the laws of chemical action, and then treat of the simple substances or agents, which are imponderable, such as light, heat, and electricity, and afterwards of those which are ponderable. He then proceeded to explain and illustrate chemical action.

Chemical action is produced by chemical affinity, and is known by the alterations which take place when two or more bodies are brought into contact. The chemical action of two bodies is supposed to be mutual and equal. Thus when lime unites with muriatic

acid, giving out its carbonic acid, the affinity of the lime for the muriatic acid is equal to that of the acid for the lime. The difference between chemical affinity and cohesive affinity is, that the former exists between the particles of dissimilar bodies, and the latter between the particles of the same. body. Thus the particles of iron are united into masses by cohesive affinity, and the muriatic acid or carbonic acid combines with lime by chemical affinity. Chemical action is accompanied by several remarkable circumstances; one of the most conspicuous of which is an alteration of temperature. Thus by mixing sulphuric acid and water, such a quantity of heat is given out, that ether boils by being immersed in the mixture. The Professor mixed sulphuric acid and water, and plunged in it a small glass tube containing ether, which almost immediately boiled up so as to be perceptible in every part of the chapel. He then mixed sulphate of soda, we believe, with nitrat of ammonia; the two combined, and so great a degree of cold was the consequence, that a small portion of water contained in a glass tube was frozen, to the admiration of all the spectators. Here, then, was the proof of change of temperature accompanying chemical action. But this is not the only accompanying circumstance. The sulphuric acid, diluted with water that gave out heat, at the same time diminishes in volume; so that if measured after being mixed, the combined substance would be found to occupy less space than the two did when separate. This may be considered as an approximation to the solid form; and on the other hand, when the change is from solidity to fluidity, cold is produced. A change of form also very generally accompanies chemical action. Fluids become solids, and solids become fluids.

Nay,

even two imperceptible gases when united form a solid. The Professor placed some volatile akali in one flask, and muriatic acid in another; he adapted one end of a

glass tube to the mouth of each flask, and he passed the other end of both into the opposite ends of a glass cylinder; the heat of a spirit lamp was then applied to the bottom of each flask, and the invisible vapour arising from the ammonia and from the muriatic acid meeting in the glass cylinder, became immediately white and flaky, so that the cylinder, from being transparent, was soon rendered opaque, and there was found a white flaky substance deposited at the bottom. This substance was sal ammonia. The Professor then illustrated chemical action, by the effect of air on iron; and stated that when iron rusted, only the oxygen of the atmosphere was absorbed, while the rust had hardly any of the properties of the metal; that it was specifically lighter, had no longer any lustre, and was not attracted by the magnet; he then beautifully remarked that this rusting of iron must have been perceived from the earliest ages, and, if attended to, would have led to the discovery of the compound nature of the atmosphere, and not have allowed this gem of science to have remained undiscovered till the eighteenth century. Another circumstance which frequently attends chemical action, is change of colour. Two pieces of copper were plunged in nitric acid, which after a short time, became of a deep blue, owing to the decomposition of the copper. Prussian blue was precipitated by a mixture of two fluids that were almost colourless, which was an instance of a coloured solid produced by mixing two colourless fluids. A piece of indigo was plunged in a solution of chlorine, and became perfectly colourless. This was a good illustration of of the bleaching power of this substance; and Mr. Phillips remarked, that by introducing it into bleaching, this operation was now performed in a few square yards, and but for this discovery it would have required as many acres. Chemical action or union is further accompanied by a total change of character, and

sometimes by a change which, prior to experience, it was impossible to imagine. Thus sulphuric acid and potash, both dreadfully acrid substances, destroying our clothes and flesh, when applied to them, become, when united, sulphate of potash, a harmless, almost tasteless salt, and so little acrid that it is employed as a medicine. Another circumstance which sometimes accompanies chemical action, was detonation; this effect the Professor showed by making use of a small quantity of detonating silver; but this phenomenon was one, which, from the danger of the experiment and of examining it, was not yet fully explained. The following, therefore, were the circumstances which he described as accompanying chemical action: Change of temperature; Change of volume; Change of form; Change of colour.

The subject, we understood, is to be continued.

In conclusion we must observe, that we are extremely well pleased that the Mechanics have obtained so able a Lecturer. Mr. Phillips is distinct in his enunciation; he is a neat and skilful experimenter, and he was careful to repeat every sentence which had the character of an axiom. The zeal and attention which his audience displayed; the well-merited applause they bestowed on various parts of his discourse; and the repeated clapping of hands which were heard at its close, must have convinced him that his pupils were highly delighted, and that they merit his care. For their sakes, we could have wished that a more rigid logic had been observed by Mr. Phillips in his division of the subject, and in some of his expressions. In one part of his Lecture, he spoke of fire as a simple substance; and in another, described light and heat, which constitute fire, as distinct substances. That they are distinct and separate, whether called agencies or substances, is abundantly evident. The warm breeze from the south brings no light with it;

on the contrary, the flash of the gun is seen even far beyond the range of the shot it hurls on a foe. We see a vivid streak pass rapidly through the clouds, but know not, till the bolt falls on our houses, that it has been accompanied by heat enough to melt iron. Light affects only the eye; is imperceptible by any other organ; and, perhaps, the eye is the only part of the body that does not convey to us the sensation of heat or cold. Heat and light, therefore, are perfectly distinct;. and fire, which in common language signifies a union of both, should never, even for a moment, be spoken of by scientific men as a simple or undecompounded sub

stance.

We beg leave also to suggest to Mr. Phillips, that chemical properties are as much natural as any other properties. They are all natural, and one part of the whole ought not to be placed in contrast or opposition with the other. The chemical properties of bodies are distinguished from their mechanical properties, or from those which are commonly and generally observed, as their weight, colour, and texture; but both the mechanical and chemical properties of bodies are equally natural.

Again, we are not quite clear as to Mr. Phillips's distinction between chemical affinity and cohesive affinity. The former being, according to him, the affinity be-tween the particles of different substances; the latter, that power which combines the particles of the same substance into massesBut copper and zinc are different substances; and, according to Mr. Phillips's definition, should only be sensible to chemical affinity; but they, as well as all the metals, when alloyed together, and many other different substances, can exist combined together into masses. The very substance Mr. P. was operating on should have dictated a different, or at least a more cautious language. Carbonic acid and lime are surely very different substances, but they exist combined into masses. Nay, lime,

when pure, assumes the character of a powder; and it would seem necessary, that the acid, or some other different substance, should be combined with it to give it solidity. Cohesive affinity is not, therefore, confined to the particles of the same substance, but belongs also to the particles of different substances; and there is no ground for the distinction which Mr. P., in imitation of other Chemists, laid down.

We make these few remarks in no spirit of hostility to this excellent Lecturer, but merely to put him on his guard, that he may not be led away by the slang of scientific men. It is incumbent on those who teach, to do it honestly and conscientiously. They are liable, of course, like their scholars, and other men, to numerous errors; but they are bound, at least, to think what they teach, to have an honest conviction of its truth, and not to repeat, like parrots, the words they may have heard. We should make a much more rapid progress in knowledge, were those who make it their business to instruct us, only to give themselves the trouble to examine the meaning of the words they repeat to us.

SECOND LECTURE. WE attended the second Lecture of Mr. Phillips, on Wednesday last, and are pleased that we can say as much in praise of it, as we have already said of the former. The Lecturer enters at once with spirit into his subject, having about him none of the dandyism of science, and desirous only freely and frankly to impart instruction. Referring to his former Lecture, he said, he had partly explained chemical action, and had shown that no matter was lost. Combustion, which appeared the consumption of a body, in fact, converted it into a gaseous product; and it was possible that the coal which we now consumed might hereafter return to the same state, and by its renewed combustion warm future generations. He before explained the circumstances which accom

panied chemical action; he would now advert to some circumstances which modify and control it. Heat, he showed, modifies it. Thus there are some substances which have no effect on others, unless a considerable degree of heat is applied; when this is the case, they decompose them. He illustrated this general fact by several experiments, only one of which we can mention. Oxygen and hydrogen gases were mixed in the requisite proportion to form water, but they had no effect on each other till flame was applied to them, when they instantly combined, with a loud explosion. Another circumstance which modifies chemical action, is the cohesion of bodies. Nitric acid, for example, has no effect on adamantine spar, or common-pipe clay, both of which are nearly the same substance, chemically speaking; but if the cohesion of these substances is destroyed, as it is by their being combined with some other substance, then they will combine with nitric acid: thus showing that the attraction of cohesion modifies chemical action. Marble is more quickly dissolved, if first reduced to powder, because a larger surface comes in contact with the solvent. The same principle explains why agitation promotes chemical action. A piece of blue vitriol, in water, coloured only the water immediately above it, but by stirring it the whole water came in turn in contact with it; the blue vitriol was more rapidly dissolved, and the whole of the water was coloured. It is sometimes the case that the chemical action of two substances on one another does not take place without the addition of a third. Thus, for example, however water and oil may be agitated together, they do not combine; but add to them a solution of an alkali, and they combine immediately. Advantage has been taken of this principle in many of the arts; and by means of it oil actually is united with water, and forms the well-known and very useful substance-soap. Another

circumstance which we shall state here, though the Professor mentioned it later in the evening, which modifies chemical action, is voltaic electricity. Copper held in solution by an acid, is not precipitated by silver; but if the silver be placed in contact with iron in the solution, thus forming a voltaic circle, copper is precipitated on the sil

ver.

The Professor then proceed ed to illustrate the two great laws of chemical action, single and double elective affinity. Thus nitric acid dissolves lime, iron, and copper; and this it does by single affinity; but it has a stronger affinity for one of these bodies than for the others, and this is elective affinity. If 100 parts of nitric acid be added to 100 parts of lime and 100 parts of copper, it does not take 50 of each, but unites with the whole of the lime, and leaves the copper untouched. In consequence of single elective affinity, the Chemist is enabled to produce single decomposition. Lime precipitates copper from nitric acid by combining with the latter. But in double elective affinity, two compounds are decomposed, and two others formed. If sulphat of iron, a compound of sulphuric acid and iron, be added to nitrat of lime, a compound of nitric acid and lime, the lime separates from the nitric acid and combines with the sulphuric acid, while the nitric acid and iron form nitrat of iron. This principle of double decomposition is not a matter of scientific curiosity merely; it is of essential use in the arts. By mixing sulphat of iron and tincture of nut-galls, the calico-printer forms his black-dye; and by a similar operation ink is made. Acetat of alumina is employed by calico-printers; but acetic acid, or vinegar and alumina, cannot be made to combine directly. Alum, however, is sulphat of alumina; and a solution of this, added

to

acetat of lead, precipitates a sulphat of lead, while the acetat of alumina remains in solution. This is what the calicoprinters want, and this process is what they actually perform. Mr. Phillips illustrated all these prin

ciples by numerous and plain experiments; so that, we believe, not one person could fail in comprehending his meaning. At the conclusion, he announced his intention to touch briefly, in his ensuing lecture, on the doctrine of definite proportion, and on the atomic theory. To the former we have no objection: it can be made palpable without adopting the latter; and we would, therefore, entreat him to reflect before he involves us too deeply among imperceptible atoms. However he may adopt the prevailing opinions on this subject, we are quite sure he is a person of too good sense to make theories of this nature a prominent feature in lectures for Mechanics. On the contrary, he shows a disposition to teach them those principles which are applicable to the purposes of life; and one fact which they can turn to account, is of more value to them than all the theories of Mr. Dalton and Berzelius.

At the close of the Lecture, Dr. Birkbeck announced, that Sir F. Burdett had given the Institution 100 guineas; and the Society of Arts had presented it with a complete copy of their Transactions. We are extremely happy to see the Institution thus increasing in wealth, as it goes on increasing the stock of information.

PROGRESS OF SOCIETY.

DURING the Lecture at the Mechanics' Institution, on Friday se'nnight, Dr. Birkbeck told the following anecdote. He was discoursing of the elasticity of the atmosphere, and showing that by its pressure on the surface of fluids, they would rise only to a certain height. The principle by which this fact was explained was unknown to Galileo. The pumpmakers of Florence applied to him to know why the water would not rise higher than thirty-three feet, when the Grand Duke had commanded them to raise it upwards of sixty. Galileo believing that fluids only rose, at any time, on the principle of nature, abhorring a vacuum, answered that her abhor