I was led into the following train of investigation from observing, that, when minute quantities of certain substances were dissolved in alcohol, and the liquid was acted on by a moderate voltaic power, evident signs of decomposition were exhibited by the evolution of elastic fluid at the negative pole. In investigating the nature of the changes produced, I was farther led to examine the action of voltaic electricity on a variety of alcoholic solutions, and also the agency of more powerful galvanic batteries on pure alcohol and on ether; and, ultimately, I was conducted into a field, into which I should have hesitated voluntarily to enter, namely, the voltaic decomposition of aqueous solutions, which has recently been investigated with so much success by a distinguished cultivator of science. In the following paper, it will be my object to give some account of the experiments which I have made on these different subjects, and of the results and views to which I have been led.

For a long time I was anxious to know the rate of expansion of the common building-stone of this neighbourhood, as it is not given in any of the tables of the expansions of substances, because I have sometimes thought that the vertical cracks frequently seen intersecting rubble walls might arise from the contraction caused by a diminution of temperature. During a long-continued and severe frost which occurred in 1826, I thought the rents in a considerable stretch of wall, which I passed at all seasons, appeared more open than usual. This, however, was merely conjectural, and I paid no more attention to the subject until 1830, when, as I mentioned in a notice on the commencement of my experiments read at the meeting of the British Association in September last, an interdict of the Dean of Guild Court of Edinburgh rendered the rate of expansion of stone a matter of more importance than merely a curious philosophical speculation.

Among persons interesting themselves in the progress of British manufactures, it can scarce fail to be known, that Mr Neilson of Glasgow, manager of the Gas Works in that city, has taken out a patent for an important improvement in the working of such furnaces as, in the language of the patent, “are supplied with air by means of bellows, or other blowing apparatus.” In Scotland, Mr Neilson's invention has been extensively applied to the making of cast-iron, insomuch that there is only one Scotch iron-work where the invention is not in use, and in that work, apparatus is under construction to put the invention into operation.

Few poisons are of greater interest, in a historical or scientific point of view, than Hemlock. It has been known ever since the most classic periods of antiquity, being generally believed to have been the ϰωνϵιον of Nicander and Theophrastus, and commonly thought to have been the poison with which state-criminals were despatched in ancient Athens. Since that period it has occupied a prominent place in all works on Toxicology; and it has been immemorially familiar as a deadly poison to the vulgar in every part of Europe, where there is scarcely a country or even a province which does not produce it in abundance. For nearly a century, too, since the writings of Baron Storck of Vienna in 1762, it has been constantly in the hands of the physician as a remedy, and has been currently employed at different times in the treatment of some of the most common, as well as in some of the most malignant, of all the maladies to which the human body is liable.

The power of making such a representation of any object, as shall give a distinct idea of its form, is a faculty which artists possess in different degrees of perfection. The principal difficulty is, to get a first delineation of any subject; from this a copy may be made in various ways, with less exertion of talent than was required for the composition of the original.

Various geometrical and optical inventions have been proposed to assist the artist in making an outline of an object which he wishes to represent. The Reticulated Square and other contrivances, for placing every point of the thing to be represented in its proper place in the picture, belong to the first class; the Camera Obscura and the Camera Lucida to the second. When a design is to be copied, a different kind of contrivances will in general be more convenient. It is only of these that I propose to treat here.

The few facts we possess relative to the chemical agency of atmospheric electricity, and a certain degree of obscurity connected with these facts, as pointed out by Mr Faraday, in commenting on the late Mr Barry's results, published in the Philosophical Transactions for 1831, have induced me to institute some experiments on the subject, with the hope of acquiring additional information.

Reflecting on the manner in which, in certain instances, the great experiment of Franklin, in apparent proof of the identity of common and of atmospheric electricity, had been repeated, especially in our own country; reflecting also on the experiments of M. Colladon on atmospheric electricity, made by means of a lightning-conductor,—it appeared to me not improbable that results might be witnessed of some interest by substituting for an electrical kite, the means employed by Mr Barry, an insulated wire raised a few feet above the summit of any building of moderate height.

1. The first series of these researches, in the exact form in which they are printed, were laid before the Royal Society on the 19th January 1835. The whole of the experiments there described were made, and the paper written and printed, within a space of time little exceeding two months. This haste, unfavourable to composition, I considered as a less evil than postponing for a period of time, which must have been considerable, the publication of a class of facts which might be said almost to embrace a new science. The professional duties which pressed upon me during the whole continuance of those experiments, then called imperatively on my attention, and during the remainder of the Session my time was devoted to them. The summer I devoted to a foreign excursion, some of the results of which I afterwards digested; and it was not till the commencement of the winter session which has just closed, that I prepared, with a fresh stock of health and spirits, to reinvestigate the whole subject of the Polarization of Heat, and to assign numerical values to the effects, whose existence I had before been contented to prove.

In entering on a question which may be said to occupy a portion of the debateable land between Physiology and Metaphysics, it seems, in the first place, necessary to state with precision the nature of the difficulty, which has long been felt on this subject, and endeavour to determine the degree to which it is reasonable to expect, that this difficulty may be removed; and on these points there is such a discrepancy of opinion, even among the latest and most esteemed authors, as obviously to make farther inquiry desirable.

No one can be more thoroughly convinced than I am, of the utter futility and absurdity of all attempts “to shoot the gulf which separates the sensible world from the sentient soul.” In all our inquiries in the Physiology of the Nervous System, as connected with mental acts, we must keep in mind, that the end of these inquiries can only be, to determine the physical conditions under which the different mental phenomena take place; and those under which, when they have taken place, they affect the different organs of the body. The question, how it comes about, that when those conditions are fulfilled, these results follow, must be held, in every case, to be beyond our powers.

Payne Knight, no mean name among philologers, after a masterly and convincing proof, that neither Zenodotus nor Aristarchus, the great critics of the Alexandrian school, could be acquitted of the charge of “scarcely credible ignorance” of the primitive form of the Homeric language, thus proceeds :—

“The grammarians and critics of Alexandria were all guilty of the same fault. They never investigated the original sources of the language, but classed among anomalous dialects and poetic licenses every thing that was not in unison with their own usual style of speaking. In their age there existed many clews to the inquiry, which have now disappeared, but which, at that time, might easily have been found in written records, and in the rude and semi-barbarous languages of Italy and other countries adjacent to Greece. Had any one, however, suggested to Aristarchus that the true form and character of the Homeric dialect was to be extracted from the Latin, Tuscan, or Oscan languages, he would in my opinion have been as much astonished as if he had heard of the claims of the Irish antiquary, who affirmed that the Homeric poems had been translated furtively from the “Gaelic into Greek.”