70 Intelligence and Miscellaneous Articles. 



buttery E' on board the repairing-boat. This method will always 

 be found of great use iu all eable expeditions, as it can be applied 

 without difficulty to the longest cable. 



COSMICAL DETERMINATION OF JOULE'S EQUIVALENT. BY PLINY 



EARLE CHASE, LL.D., PROFESSOR OF PHILOSOPHY IN HAYER- 



FORD COLLEGE*. 



In estimating heat of dissociation, Pfaundler has shownt that the 

 mean should be taken between the temperatures of incipient and of 

 complete dissociation. On this principle, in expressing the tempe- 

 rature of water-crystallization we should have regard to all stages 

 of the expansion in molecular rearrangement, and take the mean 

 (36°-6 P. = 2 C, 6) between the temperatures of greatest density 

 (4°-6) and of complete crystallization (0 D, 6). So long as water 

 continues to condense, its tendencies are centripetal and polar; 

 while it is expanding, they are centrifugal and equatorial. The 

 thermodynamic relations between heat and work should be shown 

 in the comparative motions and temperatures of polar and equato- 

 rial waters as surely, and with as abundant facilities for accurate 

 measurement, as in the experiments of the laboratory or in the pro- 

 cesses of the workshop. 



Johnston's Physical Atlas gives 82°-6 P. (2S°-1 C.) as the 

 mean temperature of the oceanic warmth-equator. This indicates 

 a polar-equatorial difference of 82°-6 to 35°-6 P. = 47 J, or 28°-l 

 to 2° C. b= 26*1 calories. The difference in gravitating measure 

 may be readily deduced from the difference of motion. The velo- 

 city of equatorial rotation is 1525' 78 feet, which represents a vir- 

 tual fall of f^" 7 8 Yx 16-044 ft. =47 J. Hence we find 

 V 32-088/ 



J = 771* 81 6 foot-pounds ; calorie =423-44 kilogrammetres. 



ON SUBSTANCES POSSESSING THE POTTER OF DEVELOPING THE 

 LATENT PHOTOGRAPHIC IMAGE. BY M. CAREY LEA, PHILA- 

 DELPHIA. 



About three years since, I communicated to Sillimans American 

 Journal the results of a long series of studies on development. At 

 the time when these were undertaken there were but four sub- 

 stances known to possess the power of development :■ — ferrous sul- 

 phate, gallic acid, and pyrogallol, which had been long known to 

 have this property; and hseinatoxylene, which I had some years 

 before added to the number. 



The studies made three years ago prove that the power of deve- 

 lopment, so far from being possessed by this small number of sub- 

 stances only, extends to a large number of chemical compounds, 

 and is exhibited by many cuprous salts, by several vegetable acids, 

 * Communicated to the American Philosophical Society, April 16, 

 1880. 

 t Pogg. Ann. 1867, exxxi. p. 603. 



