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1799, he read a paper entitled “Experiments and observations on the power of fluids to conduct heat, with reference to Count Rumford's seventh essay on the same subject.”*

He seems evidently to have made up his mind at once that Count Rumford had drawn a wrong conclusion from his premises, and we see in the reasoning much minute ingenuity and acuteness. As an example of his mode of experimenting and reasoning, the following may be given, p. 381.

Exp. 3. Took an ale glass of a conical figure, 21 inches in diameter, and 3 inches deep; filled it with water that had been standing in the room, and consequently of the temperature of the air nearly

Put the bulb of a thermometer to the bottom of the glass, the scale being out of the water; then having marked the temperature, I put the red-hot tip of a poker half-an-inch deep into the water, holding it there steadily about half-a-minute; and as soon as it was withdrawn, I dipped the bulb of a sensible thermometer about inch, when it rose in a few seconds to 180.°

TEMPERATURE.
At Top.
Middle.

Bottom.
Before the poker was immersed

479 180°

47°
5 min.

100°
60°

473° 20

70°
60°

49°
1 hour
55°

520" After other experiments he says, p. 385, “We must conclude, therefore, that the quick circulation of heat in water over a fire, &c., is owing principally to the internal motion excited by an alteration of specific gravity; but not solely to that cause, as Count Rumford has inferred.”

A very simple and ingenious experiment is related on the same page. He mixed hot and cold water, stirred for half-a-minute, and tried if the upper part became hotter than the lower, it

Time.

* Same vol., p. 373.

did not do so, on which he says, “ If the particles of water during the agitation had not actually communicated their heat, the hot ones ought to have risen to the top, and the cold ones subsided, so as to have made a material difference in the temperature.” This shows, that even at that period he was accustomed to think habitually of matter as decidedly atomic in its constitution.

On the theoretical conclusion to be drawn here, we find his genius taking the lead; he is accurate in spite of the rudeness of his experiments. He concludes that water conducts heat a little, and that the expansion of water is the same both above and below the point of maximum density. But when he comes to determine the precise place at which that point is found, as it is a matter of experiment, and cannot be got by the mind only, he is at fault; in subsequent experiments learning to become accurate.

He seems to have lowered the point to 36°, and afterwards considered it 38°, the point now apparently fixed on is 39°, or 39.101. (Playfair and Joule.) Dr. Hope's experiments gave it as between 39 and 40 degrees. In this investigation Dalton's mind again analyses itself, dividing to great clearness of conception on the one side, and carelessness of minute observation on the other.

In 1830 on reading over some old letters which he was arranging, he found one from Dr. Hope, saying, “notwithstanding the caution you gave me, I venture to publish my pamphlet on the contraction of water by heat,” Dr. Dalton said, “aye, he had the advantage of me there, but not so much as it appeared at first sight.”

In this paper he makes an observation on the power of capillary tubes to prevent the freezing of water, a circumstance which has not been thoroughly inquired into, nor the cause assigned its proper place.

In May, 1800, Dalton was elected secretary of the Literary and Philosophical Society of Manchester, in the

F

air."

place of Dr. William Henry, and having as his colleague Dr. Hull. This office he retained until the year 1809, when he was made vice-president in the room of Dr. Roget, who then lived in Manchester. Soon after, on June 27th, he read to that Society, “Experiments and observations on the heat and cold produced by the mechanical condensation and rarefaction of

Here by well devised experiments he endeavoured to shew what however had been before held by Lambert, Saussure, and Pictet, “ that the capacity of a vacuum for heat is less than an equal volume of atmospheric air, and that the denser air is, the less is its capacity for heat,” indicating a mode of ascertaining “the absolute capacity of a vacuum for heat," and " likewise the capacity of the different gases for heat by a method wholly new.”

An important result of these experiments was, that the temperature of air mechanically compressed to one-half its volume was raised 50°. This, although much underrated, was the first numerical result of importance on this subject. p. 524.

In this paper we find that he had ascertained that gases expand 1-10th of their volume nearly for 50° of heat, or nearly 1-500th of their bulk, a subject which he treated of at a later period.

Whilst engaged in teaching at the academy in Manchester, his classes or scholars seem to have been as miscellaneous as they had been at Kendal. We may infer this from the appearance of an English grammar, the preface of which is dated March 10th, 1801. He seems to have looked on this as a recreation, but he never afterwards appears to have had recourse to literature for amusement or for variety. As he has never been looked on as a grammarian, it may be of some interest to see what his views on such points were.

He says, p. 8. “It may be taken as an axiom that all time or duration in the strict sense of the terms, is either

* Meń., Vol. V., p. 515.

past or future.

But for the purposes of speech we must have a present time of some duration, which must necessarily be comprised of a portion of past and a portion of future, having the present, now or instant, as a boundary between them. Its length may be what we please to make it.

“ Grammatically speaking therefore, there are three times, present, past, and future; though strictly and mathematically speaking, we can admit only two, past and future. Moreover we find it expedient in the course of conversation, not only to mention actions as whole and entire, but also their commencement, their being in a passing or middle state, and their termination; accordingly our language furnishes us with four forms of speech for each of the times or tenses, which are exemplified in their proper place, both for the active and passive verb, with appropriate names to them.”

His active verb is given thus :-
Indicative mood.

Present time.
I serve, &c.
Beginning present.
I am about to serve, &c.
Middle present.
I am serving, &c.
Ending present.
I have served or been serving, &c.
Past time.
I served, &c.
Beginning past.
I was about to serve, &c.

Middle past.

I was serving, &c.
Ending past.
I had served or been serving, &c.
Future or present time.
I shall, will, may, can or must serve, &c.

Beginning future or present.
I shall, will, may, can or must be about to serve, &c.
Middle future or present.
I shall, will, may, can or must be serving, &c.
Ending future or present.
I shall, will, may, can, or must have served or have

been serving. In

grammar it is difficult to have absolutely new ideas, the subject has been so belaboured, and at the same time it is not easy to keep rigidly to any system proposed, so many of the treatises have wanted clearness. We may see that in that department Dalton was inclined to be an innovator, although he has not the honor of being a discoverer, indeed his mind was much too rigid to be inclined to yield to all the flexions and variations of a subject so bordering on metaphysics as grammar.

Horne Tooke is the writer which he most admired on that subject, using sometimes his very words, although not in all things following him. But innovators are more dangerous in grammar, and are less easily received, than in the physical sciences which have no ancestry.

Some years afterwards he went into the shop of the publisher of his grammar, and asked for a copy; he was told they had none, but insisting on it, a parcel of them was found in some dusty corner, very few having ever been sold. Still he assures us that a Sheffield man had published it some years later as his own, with some additions. In October of the same year he read a paper

which occupied three evenings of the Literary and Philosophical Society. It is composed of four “ Experimental essays on the constitution of mixed gases; on the force of steam or vapour from water and other liquids in different temperatures, both in a Torricellian vacuum and in air; on evaporation; and on the expansion of gases by heat.” (Mem. Vol. V., p. 535.)

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