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of the length is T | T , that of the specific gravity from tem-pering consequently ^ ; but the hammering increases it toJ,. The expansion of water by freezing presents a similarphenomenon.
On the flexure of wax and metal in cooling.
Nich. 8 . IV. 170.
Hatchett. Ph. tr. 1803. 118.
Found that gold debased with impure copper becamebrittle when cast in moulds of sand, but was renderedductile when cast in moulds of iron. The specific gravityof standard gold when cast in iron was also greater thanwhen cast in sand, in the ratio of 290 to 2S9, and in oneexperiment of 6 1 to 60. The metal cooled more rapidlyin sand. In some cases the evolution of gas may, perhaps,be concerned in affecting the specific gravity.
Communication of Heat by contactand in general.
La Chapelle on a bar of steel becominghot when withdrawn from boiling water.
A. P. 11. 25.
Ilomberg on the increased heat of the bot-tom of a vessel when removed from thefire. A. P. 1703. H. 24.
This appears to be a fallacy: with a clean surface itmay easily be detected.
Martine’s essay on the heating and coolingof bodies.
Richmann on the laws of the decrement ofheat. N. C. Petr. 1 . 174. LI. 172 .
Makes its decrement as the surface exposed and as thedifference of temperature conjointly.
Richmann on the cooling bodies in air.N. C. IV. 241.
Insists that a ball of metal 4 inches in diameter cannotbe heated by boiling water beyond 207° : and the ex-periments seem to indicate, that even in cooling its tem-perature is always lower, which indeed is the only pointthat can affect the theory. Brass and copper retain heatlonger than iron, iron than tin, and tin than lead.
Lambert on heating and cooling. Act. Helv.
II. 172.
Lambert Pyromctrie.
Darwin, l’h. tr. 1757. 240.
Supposes steam to float in air, and retain its heat.
Musschenbroek’s table of the time of heatingof different bodies. Introd. II. 078.
Euler on the motions of fluids from heat.N. C. Petr. XI. 232. XI1L 305. XIV.070 . XV. 7, 219.
Braun on the communication of heat. N. C.Petr. XII. 289. Roz. I. 1.
Confirms Richmann's experiments on boiling water andalcohol: but finds the result different with wine and oils.For these, however, the boiling point must be variable,and the result is of no value.
Roy. Ph.tr. 1777- 720.
Observes, that water is a very bad conductor of heat.
Erxleben on the laws of heat. N. C. Gott.1777- VIII. 74.
Exceptions to the law of Newton, Itichmann, andLambert.
Achard on the conducting powers of gases.A. Berl. 1783. 84.
A chard’s comparison of heat and electricity.Roz. XXII.245.
Achard on the cooling of bodies in air ofdifferent densities. A. Berl. 1785. 24.Makes no general conclusions. The difference betweenthe rates of cooling in airexhausted to £ and to * was some-times imperceptible, and scarcely in any case
Fordyce’s experiment on heat. Ph. tr. 1787.310.
Two equal cylinders of pasteboard were inclosed ineider down under glass, one was covered with iron,the other with pasteboard, both painted with the sameblack paint, which was exposed to the sun's rays: thepasteboard never transmitted a heat of more than hopthe iron 121 ° : the iron also retained its heat much thelongest.
Sir B. Thompson on heat. Ph. tr. 1780.273.Ess. II. viii. Report. IV. 30. Gilb. V.288.
The conducting power of mercury being 1000, that ofmoist air was 230, of water 313, of common air 80.4 1 ,of air j as dense so. 23, of air ^ as dense 78, of avacuum 55. The two last numbers, compared with theconducting power of common air, appear to indicate aformula of this kind, 55 + 25.4ifb, d being the density.,,compared with that of the atmosphere.