1815.] Dr. Joseph Black. S27 



respecting the nature of steam that led Mr. Watt to his great 

 improvements on the steam-engine— improvements which liave 

 been of incalculable benefit to the manufactures of Great Britain. 



Dr. Black was the first person who pointed out that evtry sub- 

 stance is possessed of a peculiar specific heat, or that ilifferent 

 bodies have different capacilies for heat. This subject was after- 

 wards further investigated by Dr. Irvine, of Glasgow, and by Mr. 

 Wilcke, of Stockholm. 



A very short paper by Dr. Black was published in the 65th 

 volume of the Philosophical Transactions, for the year 1775, 

 giving an account of some experiments showing that recently 

 boiled water begins to freeze more speedily than water that has not 

 been boiled. He found that if the unboiled water be continually 

 stirred, it begins to freeze as soon as the boiled water. He gives 

 the following explanation of the phenomenon. Water by boiling is 

 deprived of a portion of air. When exposed to the atmosphere it 

 begins to absorb this air, and continues to do so till it has recovered 

 its original quantity. This absorption produces a disturbance in the 

 water, not indeed sufficient to be perceived by the eye, but suffi- 

 cient to prevent it from becoming colder than 32°, without begin- 

 ning to freeze. 



The only other paper written by Dr. Black was published in the 

 second volume of the Transactions of the Royal Society of Edin- 

 burgh. It is an analysis of the Geyzer and Rikum springs in 

 Iceland. A quantity of the water of these springs was brought 

 from Iceland by Sir John Thomas Stanley, and sent to Dr. Black. 

 This paper may be taken as a model of the proper manner of 

 examining mineral waters. The following were the constituents 

 found in 10,000 grains of each of these waters : — 



Rikiira. Geyzer, 



Soda 0*5 1 gr 0*95 gr. 



Alumina . . . . ' 0*05 0'4S 



Silica 373 5-40 



Common salt 2*90 2- 1« 



Sulphate of soda 1-28 \'A6 



8-47 10-75 



Article II. 



On tlw Doctrine of Fluxions. By Alexander Christison, Esq. 

 Professor of Humanity in the University of Edinburgh. 



(To Dr. Thomson.) 



MY DEAR SIR, 

 It is very much to be regretted that many students at the univer- 

 sities of North Britain accjuire no knowledge of llu,\ions. They 



