316 Extracts from the Journals. [Oct., 



THE ABSORBENT POWERS OF DIFFERENT EARTHS. 



BY PROF. LESLIE. 



[On looking over some old papers communicated for the Annals 

 of Philosopky, for ISOI, we stumbled upon an interesting paper 

 on the absorbent power of earths, by the celebrated Prof. Leslie. 

 We were perhaps more interested than we should have been, had 

 we not recently been engaged in experiments of a similar cha- 

 racter. We were pleased to find Prof. Leslie's observations of 

 clays and soils which have been ignited, to agree with our own. — 

 Editor.'] 



Mr. Leslie, who is deservedly known to the world by his pho- 

 tometer and hygrometer, has applied the latter instrument to some 

 investigations hitherto neglected by those who have studied the 

 affections of different bodies to humidity. 



Having discovered that animal and vegetable matters, like the 

 saline and deliquescent substances, attract humidity by a force al- 

 together distinct from capillary absorption, he was induced to try 

 whether the earthy bodies under the same circumstances, would 

 not exhibit analogous properties. These experiments, of which 

 we shall give a short account, led to the conclusion, that all earths 

 and stony bodies eminently attract moisture from the air, and this 

 with different degrees of force, modified also by temperature, 

 which affects the measure of all cojubinations. 



The experiments were made in the following manner: the 

 earths to be examined, grossly pounded, were dried thoroughly 

 before a good fire, and afterwards kept secluded in phials from the 

 air and moisture, till they were perfectly cool. They were then 

 spread upon a saucer, in which was placed a hygrometer, and the 

 whole covered with a small receiver. In a few minutes the in- 

 strument marked the highest degree of dryness produced; whence 

 was deduced the desiccating power of the included earth, or its 

 attraction for humidity. In this mode the following results were 

 obtained, at the temperature of 16 deg. Centigrade: 



Freestone, - - - - 37 deg. 



Fine sea-sand, - - - -~ 40 

 Marble, ----- 47 



Common clay, - - - - 68 



Sea-sand lately cultivated, - - 72 



Sandy schist, - - - - 75 



Bog earth, . - . . 77 



Rotten whinstone, - - - 78 



Garden mould, - - - SO 



