398 



Intelligence and Miscellaneoiis Ai-ticles. 



bert, E. Cephalaspis, Salter, E. tetragonophthahnus, Fischer, E. re- 

 mipes, Dekay, and E. lacusiris, Harlan, complete the list of the 

 known species of this genus. 



9. " Description of a New Fossil Crustacean from the Lower 

 Greensand of Atherfield." By Charles Gould, Esq. Communicated 

 by Professor Huxley, F.G.S. 



This is a macrourous crustacean, of rare occurrence, named by 

 the author Mithracites Vectensis, and is related to the equally rare 

 Mithracia of Bell (tertiary). 



XLIV. Intelligence and Miscellaneous Articles. 



ON THE RELATIONS BETWEEN THE TENSIONS AND TEMPERA- 

 TURES OF VAPOURS. BY J. A. GROSHANS. 

 ON comparing the numbers in the Table calculated by Regnault 

 from his experiments on the tension of aqueous vapour at 

 different temper itures, I have found the following formula, — 



f-\m _ l /a- Vim 



Z»*-10O~;^6-^76O ^' 



in which a and b are two tensions expressed in millimetres, and t" 

 and t'' the corresponding temperatures. 



To see how this formula would agree with Regnault's results, I 

 calculated the following Table : — 



Tension b. 

 t^, millims. <" calculated. 



4-600 



+ 25 23-550 



+ 50 91-982 



75 288-517 



95 G33-788 



105 906-41 



120 1491-28 



121 1539-25 



122 • 158847 



150 3581-23 



175 6717-43 



200 11688-96 



230 20926-40 



121 

 120 

 120 

 1-20 

 120 

 120 

 120 

 120 

 120 

 120 

 120 

 121 

 121 



Average 120-81 



The numbers i'' and b are derived directly from the Table ; a is 

 always equal to two atmospheres = 1520 millims. 



The numbers 100 and 760 in the formula miglit of course be re- 

 placed by any numbers C^ and c taken at pleasure from Regnault's 

 Table. 



If we take, for example, ^'^=150, <*=200, and a and b from the 

 Table, place these values in the formula (1), make ^"^ = 0, and solve 

 the equation as regards c, we find c = 4-221 millims. Regnault's 

 Table gives 4-600 millims. for the tension of aqueous vapour at 0^ C. 



