rary mess house, of the farm house, and those, belonging to the Inn in the English garden, of the hospitals of La Pièta and La Miserecordia at Verona, of one, fitted up, as a model, in the house of Sir John Sinclair, Bart. in London, of the foundling hospital at London, of the military kitchen for the camp, and several others in different parts of Europe are suf- ficient to show the ingenuity and usefulness as well, as the success of his plans of reform.

In warming the habitations of men by common fires, by steam, and by smoke, though this application of the two last is quite novel, he has made the heat, produced in the combustion of fuel, pass through the several offices of cooking, boiling water, and warming rooms in such a manner, as scarcely a particle of heat is lost. He fitted a boiler at one end of one of the working halls to the house of industry in Dublin, by which steam, in conjunction with smoke, was made to warm the room, and in one of the churches of that city steam alone was made use of, which completely answered his expectations. He also formed a plan of the same kind for heating the superb new building, destined for the meeting of the Irish house of commons.*

The seventh essay relates to "the propagation of heat in "fluids." This is diversified by so many experiments and

* His plan is to confine the steam in the boiler so, that it is made to pass off by a leaden tube through the halls or rooms, in the same manner the smoke is conducted from common stoves. Care should be taken, that, instead of placing the tube or funnel horizontally, it pass through the apartment inclined, that by this means the steam, as it condenses in its passage, may run back at the bottom of the tube to the boiler. This useful contrivance may easily be applied to halls, near any great kitchen, in a manner, that would neither increase the quantity of fuel, nor make any additional trouble in the process of cooking. By this scheme, it is conceived, the commons hall at Harvard University can be heated, the hall being immediately above the kitchen; and by a little improvement in the cooking apparatus the quantity of fuel might be considerably diminished, and even this decrease of expense be converted to an increase of the comfort of those, who breakfast and dine în commons. Even in the humble habitations, provided for the poor throughout the New England towns, arrangements of this kind would be found að vantageous.

such just observations on the general economy of the universe, with all the various and beautiful changes of seasons and climates, that the mind is unwarily lead to sublime contemplation. In these, as in all his philosophical researches, he makes the most accurate experiments, faithfully relates them, makes his own reflexions, and leaves his readers to draw such conclusions, as facts will justify, without wishing them to adopt any particular theory.

The object of his eighth essay, " on the propagation of "heat in various substances," is principally to investigate the causes of the warmth of natural and artificial cloathing.

Count Rumford's ninth essay, which closes the second volume, is an "inquiry concerning the source of the heat, "excited by friction." With such a patron and assistant, as the Elector, he could easily command whatevever might aid him in his useful studies. Pursuing his official occupation of superintending the ordnance, and boring cannon at Munich, the process suggested to him many important hints relative to this subject.

An idea, that heat is caused by friction, has been entertained by many philosophers, while some have given it a different origin. But Rumford's experiments place the question in a clear light. By confining the end of a cannon, while boring, in a box filled with water, so that the operation was performed below the surface of the fluid, the heat, generated by the friction, communicated itself to the water, and, by measuring the temperature of the water at regular periods, he determined the quantity of heat, produced in the experiment, The event, as may easily be supposed, affordel him much satisfaction, and quite astonished the bystanders, who witnessed it. While the machinery was moving, the degree of heat, which the water acquired by the friction between the borer and the cannon during two hours and thirty minutes, was sufficient to make the water boil.

While upon this subject, we shall insert the substance of a "mémoire sur la chaleur, par M. le comte de Rumford, lu à la " séance publique de l'institut national, le 6 messidor an. 12,"

though not communicated to the public, till June 1804 in the "Gazette Nationale."

He has in this memoir, read before the national institute of France, of which he is a member, endeavored, with great success, to reconcile the different opinions among philosophers, some of whom consider heat, as a substance, and others, a vibratory movement of the component particles of bodies. The Count has adopted the hypothesis of vibratory movement, and concludes from his own researches, that this is alone sufficient to account for all the phenomena of heat.

The French philosophers, perceiving the difficulties, which arose from the ambiguity of chemical language, adopted the word, calorique, to express heat, whether considered as matter, or the movement of its particles; and this term will suit all opinions, leaving the question yet undecided, what is beat, and what are the certain invariable laws of its operation ?

To ascertain how extremely active this principle is, and to expose its most secret works, he contrived an instrument, very simple indeed, which he called a Thermoscope. It consists of a glass tube about 28 inches long, with the interior diameter half a line. The two extremities, ending in very thin glass bulbs of about one inch and a half diameter, are bent so, as to form right angles with the remaining part of the tube, and leaving the horizontal or middle part sixteen inches long. In this instrument is inclosed a small quantity of colored spirits of wine, and wholly defended from any communication with the external air. While it is used, the two arms are placed perpendicular, and when any warm or cold body is presented to either bulb, the other being secured from its effects by proper covering, the operation on the spirits of wine is designated by graduations on the horizontal tube.

"La sensibilité de cet instrument est si grande que, lors66 qu'il se trouve à la température de 15° à 16° du thermom "etre de Réaumur, la chaleur rayonnante de la main, quand "elle est présentée à une de ses boules, à la distance de trois "pieds, suffit pour faire avancer la bulle d'esprit de vin de

66

હૃદ plusieurs lignes; et les influences frigoriques d'un disque "métallique, noirci de quatre pouces de diametre, à la température de la glace fondante, présenté à la distance de 18 66 pouces, fair marcher la bulle dans un sens contraire, avec CC une vitesse tres-visible à l'œil.

"A l'aide de cet instrument, j'ai découvert 1°. que tous "les corps, à toutes les températures (les corps froids aussi "bien que les corps chauds), 'envoient continuellement de leurs "surfaces des rayons, ou plutôt, à ce que je crois, des ondu"lations analogues aux ondulations dans l'air, que les corps sonores envoient dans toutes les directions, et que ces ray"ons ou ondulations affectent et changent peu-à-peu les tem"pératures de tous les corps contre lesquels elles frappent, "sans être réfléchies, dans tous les cas où les corps ainsi frappes se trouvent être ou plus chauds, ou moins chauds (6 que le corps, de la surface, duquel les rayons ou ondulations " émanent.

"2°. Que l'intensité des rayonnemens de différens corps, à "la meme température, est très-différente, et qu'elle est moindre dans les corps, qui réfléchissent les rayons de lumiere, que dans ceux qui les absorbent; moindre dans les métaux, que dans leurs oxides; moindre dans les corps opaques et polis, que dans les corps imparfaitement diaphanes et non "polis.

3°. Que les rayons que les corps, qui se trouvent à la "meme température envoient l'un à l'autre, n'ont aucunc ten"dance à opérer des changemens quelconques dans les tem"pératures d'aucun de ces corps.

"4°. Que les rayons qu'un corps quelconque à une tem"pérature donnée envoie continuellement de sa surface dans "toutes les directions, sont, ou calorifiques, ou frigorifiques, "pour les autres corps, contre lesquels ils frappent, selon que " ces derniers se trouvent, ou moins chauds ou plus chauds,

que le corps de la surface, duquel ces rayons émanent; de "facon que les mêmes rayons se trouvent calorifiques pour "tous les corps moins chauds, que le corps d'où ils émanent, "et frigorifiques pour tous ceux, qui se trouvent plus chauds 66 que ce corps.

r

D'après ces faits, on pourra conclure à priori, que les corps, qui, étant chauds, envoient beaucoup de rayons ca❝lorifiques, doivent aussi, lorsqu'ils se trouvent plus froids "que les corps, qui les environnent, leur envoyer beaucoup de rayons frigorifiques. Or, c'est-là précisémeut ce, que mes

"expériences m'ont fait roir.”

Pursuing the train of his experiments with the thermoscope, he observed many analogies between the operation of heat or cold on different bodies, and the undulations, arising in the air, when any sonorous body was struck. While reasoning on the experiments and the probable similarity of the two operations, he was led to suppose, that, if the vibration or undulation in the air, caused by the percussion of sonorous bodies, could have any anology with the vibratory movement, supposed to be the hidden cause of heat, a speaking trumpet would afford some assistance in ascertaining the fact. Having placed one of the bulbs of the thermoscope at the small end of the speaking trumpet, which was well polished and bright on the inside, he applied a very thin globe of copper about three inches diameter, filled with pounded ice, at the distance of twelve inches from the other. This instrument caused the cold body to operate with triple the force on the bulb of the thermoscope.

"Pour me servir d'une métaphore un peu forte," says the Count," mais qui exprime parfaitement l'idée que j'ai conçue de l'operation méchanique dont il est question, je dirai la boule froide parlait devant la grande ouverture du <6 porte voix, pendant que la boule du thermoscope écoutait "derriere sa petite ouverture.

que

This memoir contains many other interesting experiments, relative to the facility, with which calorific or frigorific rays operate on white or black, polished or unpolished bodies. They are not confined to speculative inquiries, but are made to throw new light on the phenomena of nature, and to show how she has accommodated the nations of the earth, who inhabit a burning climate, with a defence against the intense Thus the black skin of an African enables

heat of the sun.