in six weeks, and I contrived an excursion to Deeside, before settling for the winter. I was now in close intimacy with Masson; and we discussed his topics for the Banner. In the month of November, I had finished all that I could do for the Logic, and the earlier portions were now passing through the press. It was arranged that I should review the work for the Westminster; accordingly, I received the sheets as they were worked off.

In a letter in the beginning of October, Mill was commissioned by Hickson to ask if I would prepare an article on Liebig's two books. The second, on animal chemistry, was not long out, and had been reviewed in the Quarterly by Gregory, the translator. Although I had collected a portion of my examples out of the Animal Chemistry, I did not feel qualified to review the book, still less to go back upon the Agricultural Chemistry, which Playfair had translated some time previously. I rather wished Shier to undertake something, perhaps for the Edinburgh; but Gregory had the whip hand by being able to give extracts in advance of actual publication. From seeing by my extracts the importance of the works, Mill thought it worth his while to read both for himself, and was exceedingly struck with their bold originality.

In December of this year, I became a member of the Aberdeen Philosophical Society, made up chiefly of Professors and Lecturers connected with the Colleges, with a gradually increasing number of non-collegiate members. In the following January, I gave the Society my first paper, concocted from the points elaborated in London in the summer. The topic was Heat, and the title, "An attempt to generalize and trace to one sole cause-viz., the Liberation of Latent Heat -all causes of Terrestrial Heat". Starting from the simplest case the heat of combustion,-I urged that this was a pure case of the liberation of heat latent in the oxygen of the atmosphere, and requiring to be restored, if the carbonic acid or steam, or other product had to be decomposed again. I made great use of the circumstance that the heating of solids led, first, to their liquefaction, and, next, to their becoming gaseous, while cooling reversed the process. In regard to combustion, I took notice of the circumstance that the oxygen and hydrogen that combined to form water were substances in a very high state of tension, as shown by their resisting liquefaction, while the resulting compound, steam, was readily condensed. I treated this as a general principle in connexion with the evolution and absorption of heat; being, however, well aware of such

exceptions as the explosion of gunpowder and the detonation of fulminating substances-these, indeed, being exceptional up to this hour. I took occasion to remark upon Sir John Herschel's attempt to account for the mystery of solar heat, by adducing the case of friction as an instance of an inexhaustible supply,-in fact, deriving heat, in the long run, from nothing at all. The paper was received with strong expressions of disapproval and dissent from almost every one. Dr. Gregory alone thought it contained good suggestions. Indeed, some of the points most objected to had appeared already, and gained admission into chemical treatises: I found in Turner's Chemistry that the decomposition of compound bodies necessarily involved the restoration of the heat given out in the act of combining. Some of the members had treated this, in common with the other doctrines, as a wanton anticipation of what only experiment could establish. I may add that the Professor of Natural Philosophy in King's College, Dr. Fleming, was very severe upon the criticism applied to Sir John Herschel.

Everything urged in the paper has long become commonplace, although there was a failure in leading up to the doctrine of Conservation, very soon to be established. What was chiefly wanted was the hypothetical rendering of the latent heat

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of bodies in terms of force or motion, instead of some merely structural equivalent, such as the blacksmith's experiment of hammering a rod of iron red hot had suggested. We were still some way from setting up motion in molecule as the transformation of motion in mass, and as surrendering that motion by suitable arrangements.

Winter Session, 1842-43.

My winter's work, November, 1842, to April, 1843, may be said to have comprised (in addition to the conduct of Glennie's class) the final contribution of scientific examples to Mill, the writing of the paper for the Philosophical Society, and the preparation of the review of the Logic in its entire compass for the Westminster. I felt the necessity of improving my knowledge of French, and had to devote some time to that object; the first use made of it being to read Comte's book for myself. The March (1843) number of Blackwood contained a review of the work, from which I derived my first definite impressions.

The first letter I had from Mill this year (19th January) was to the effect that he had recomposed nearly the whole of the Sixth Book of the Logic, thinking it the weakest part of the

work, but now satisfied that it was put on a level with the others.

Comte's sixth volume, a very bulky one, had not been long out, and he had made a point of completing its perusal before giving the finishing touch to his treatment of the logic of politics.

At this time, indications were given of the resolution of the leaders of the Non-Intrusion party to leave the Church rather than submit to the State trammels that had now overtaken them. While speaking with admiration of their resolve, Mill significantly suggested that, in making the contemplated sacrifice, they should see that the interests of their followers were looked to, as well as their own.

The Logic was out in March. My review appeared in the beginning of May. In a letter, dated 2nd May, Mill described the success of the book in various quarters. It was largely read both in Oxford and in Cambridge, there being a mixture of motives; some reading with a view to being instructed, others for the purpose of controversy. A more remarkable feature was its reception by the Puseyite and Catholic parties, then at the height of their ascendency. The chief outcome of this was the long article by Ward in The British Critic, which reviewed Mill throughout his whole series of avowed publi