904 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



In one of liis experiments Cullen used nitrous ether, when the heat of 

 the ah' was 53°. He set the vessel, containing ether, in one a little larger 

 containing water, and placed the two under the receiver of an air-pump. 

 On exhausting the receiver and maintaining the vessels in vacuo for a 

 few minutes, the water in the outer vessel was frozen and the ether re- 

 cipient coated with a firm and thick crust of ice. 



Dr. Cullen explains in his Essay* that he had endeavored to give a 

 notion, of tlie comparative ijower of these fluids in producing cold, by the 

 order in which he has set them down, as follows : 



1. The quick-lime spirit of sal am- 



moniac. 



2. The aether of Frobenius. 



3. The nitrous sether. 



4. The volatile tincture of sulphur. 



5. Spirits of wine. 



6. Spirit of sal ammoniac made with 



the fixed alkali. 



Cullen adds : "From the above enumeration, I imagine it will appear 

 that the power of evaporating fluids in producing cold is nearly accord- 

 ing to the degree of volatility in each." "From the fact 



that the cold is made greater by whatever hastens the evaporation, 

 and particularly that the sinking of the thermometer is greater as the 

 air in which the experiment is made is warmer, if dry at the same time, 

 I think we may now conclude that the cold produced is the effect of 

 evaporation." 



Dr. Cullen's desire to investigate this subject had been increased by 

 reading M. de Mairan's Dissertation sur la Glace, published in 1749, 

 and he had also been informed of Kichmann's researches. Eichmann 

 had taken notice of the effect of evaporating fluids in producing cold, 

 but does not impute it to the evaporation alone. 



I was fortunate in finding Eichmann's papers in the first volume of 

 the Transactions of the St. Petersburg Academy of Sciences for the 

 years 1747 and 1748, in the Congressional liibrary in Washington, and 

 I subjoin the full titles.t In the same volume I was gratified to dis- 



* Of the cold produced by evaporating fluids, and of some other means of producing 

 cold, Ly Dr. William Cullen (May 1, 1755). Published in Essays and Observations, 

 Physical and Literary. Read before a society in Edinburgh, and published by them. 

 Vol. II. 175G. p. 145. 



tG. W. Richmann's papers are four in number: 1st. De quantitate caloris, qua) post 

 miscelam fluidorum certo gradu calidorum oriri debet cogitationes. 2d. Formula) pro 

 gradu excessus caloris, supra gradum caloris mixti ex nivi et sale ammoniuco, post 

 miscelam duarum massarum aquearum diverso gradu calidarum confirmatio per experi- 

 menta. M. Inquisitio in legem, secundum quam calor lluidi in vase contenti, certo 

 temporis intervallo, in temperie aeris constantes eadem descrescit vel crescit et detec- 

 tio cius, simulque thermometrorum perfecto concordantium construendi ratio hinc 

 deducta. 4th. Tentanien legera evaporationis aqua) calidai in aere frigidori, constautis 

 temperiei definiendi. — Novi Commentarii Academia) Scientiarum Imperialis PetropoU- 

 tauae. Tom. 1, ad annum 1747 ut 1748. 



