Chemistry and Physics. 223 



gression. If the ratio of this second progression is 2, the ratio 

 of the first for air is 1*366; 1*301 for hydrogen; 1*431 for car- 

 bonic acid; and 1*415 for olefiant gas," is only approximately 

 true in the case of a large balloon and at pressures from a few 

 millimeters upward. It is not true when a small balloon is used, 

 and at small pressures it is not true of large or small balloons. 

 In small balloons the cooling effect of the last millimeter of air is 

 nearly ten times as great as that of all the rest up to atmospheric 

 pressure combined." 



The author finds that Professor Crookes's statement: "That 

 each additional diminution of a millionth would produce a 

 still greater retardation of cooling, so that in such high vacuo 

 as exist in planetary space the loss of heat — which in that case 

 would only take place by radiation — would be exceedingly 

 slow," is not true, lor the curves representing the rate of cooling 

 do not break down materially at pressures as low as a twentieth 

 of a millionth. The enormous heat-conducting capacity of gases 

 at very small pressures is shown by the curves. In the large 

 bulb used, hydrogen at a pressure of only twenty-six millionths 

 of an atmosphere transmits heat as rapidly as the ether. At 

 seventy-six millionths it equals air at atmospheric pressure, that 

 is to say it does the work of nearly two hundred thousand times 

 its weight of air. — Phil. Mac/., Jan., 1898, pp. 31-42. J. t. 



12. Conductivity qf Carbon, for Heat and Electricity. — L. Cel- 

 lier has determined the heat and electrical conductivity of carbon 

 and finds that Professor Weber's law connecting heat conductivity 

 and electrical conductivity does not hold in the case of carbon, 

 and that carbon cannot be at all compared with metals. — Wied. 

 Ann., No. 7, 1897. j. t. 



13. Determination of Relative Heat Conductivity by the Iso- 

 thermal Method. — W. Voigt describes a modification of Senar- 

 mont's method of determining relative conductivity by means of 

 the melting of a substance on the surface of the bodies. Voigt 

 uses a mixture of wax and turpentine, with Elaidinsaure in defi- 

 nite proportions, and obtains melting curves of extraordinary 

 sharpness. Double plates were employed, cut in the form of right- 

 angled triangles, with acute angles of 45°. These plates were 

 put together so as to form a right-angled parallelogram, and hav- 

 ing been cooled with the above substances were exposed to a 

 source of heat, and the angles between the melting curves on the 

 two plates were measured. The correspondance between the 

 observed and calculated values was very good. — Wied. Ann., No. 

 1, 1898, pp. 95-100. j. t. 



14. Rontgert's Original Papers on the Rontgen Rays. — The 

 original papers of Rontgen, first published in the proceedings of 

 Der WiirzburgerPhysik. Medic. Gessellsch., have been republished 

 in the current number of Wiedemann's Annalen der Physik and 

 Chemie, as leading articles. There is a quiet irony in this, as if 

 to show that Rontgen had anticipated the labors of the army of 

 investigators who have endeavored to extend his work. — Wied. 

 Ann., No. 1, pp. 1-37. j. t. 



