904 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



In one of his experiments Cullen used nitrous etber, wlien the heat of 

 the an- 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 the comparative power 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- 7. Brandy. 



moniac. 8. Wine. 



2. The tether of Frobenius. 9. Vinegar. 



3. The nitrous ?ether. 10. Water. 



4. The volatile tincture of sulphur. 11. Oil of turpentine. 



5. Spirits of wine. 12. Oil of mint. 



6. Spirit of sal ammoniac made with 13. Oil of pimento. 



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 i^roduced 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 Eichmann's researches. Eichmann 

 had taken notice of the effect of evaporating fluids in x>roducing cold, 

 but does not impute it to the evaporation alone. 



I was fortunate in fintling Eichmann's paj^ers in the first volume of 

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

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

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



*0f tlie cold produced liy evaporating fluids, aud of some other means of producing 

 cold, by Dr. William Cullen (May 1, 1755). Publislied in Essays and Observations, 

 Physical and Literary. Read before a society in Ediubra-gh, and published by them. 

 Voi. II. 1756. p. 14*5. 



tC W. Richmann's papers are four in number : 1st. De quantitato caloris, qutepost 

 miscelam fluidorum certo gradu^calidorum oriri debet cogitationes. 2d. Formul* pro 

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

 miscelam duarum massarum aquearum diverso gradu calidarum confirmatio per experi- 

 meuta. 3d. Inquisitio in legem, secundinn quam calor fluidi in vase content!, certo 

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

 tio eius, simulquo thermometrorum perfecte concordantium construendi ratio hinc 

 deducta. 4th. Tcutamcn legera evaporatiouis aqupe calida? in aere frigidori, constantis 

 temperiei deiiniendi. — Novi Commentarii Academite Scientiarum Imperialis Petropoli- 

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



