PROGRESS AMONG THE ARABS. 37 



r. Improved the hydrometer, for determining the specific 

 gravities of liquids. 



s. Drew up tables of SPECIFIC GRAVITIES (after Abur 

 Raihan, who was the first to construct them), and they 

 approach very closely to our own. In the case of mercury 

 he was more exact than we were last century. 



t. In physiology, he upheld the doctrine of the PRO- 

 GRESSIVE DEVELOPMENT of animal forms thus anticipating 

 Diderot, Lamarck, and Darwin. 



It is hardly necessary to point out that the great discovery 

 of ATMOSPHERIC REFRACTION increased the accuracy of 

 astronomical observations. 



The Arabs originated scientific CHEMISTRY it was an 

 outgrowth of the medical science at first. The discovery of 

 strong acids laid its foundations. They had already defined 

 alchemy as the science of the balance, the science of the 

 weight, the science of combustion a definition wonderfully 

 accurate. 



800. Giaber (also called Geber and Yeber), THE FOUNDER 

 OF CHEMISTRY, discovered nitric acid (aqua fortis, JE), 

 sulphuric acid, nitrate of silver, auric chloride (aqua regia, /R), 

 mercuric chloride (corrosive sublimate), mercuric oxide (red 

 oxide of mercury). His discovery of STRONG ACIDS was a 

 revolution, for most of our chemical experiments would be 

 impossible without them, and before Giaber no stronger acid 

 was known than concentrated vinegar. He set forth the 

 corrosive power of nitric acid, and how it dissolves gold 

 itself by adding a portion of sal-ammoniac thus solving 

 the problem of obtaining gold in a potable form. Giaber 

 proved that OXIDATION, or burning, INCREASES THE WEIGHT 

 OF METALS a fact over which Lavoisier will ponder nine 

 hundred years later, and by which he will be led (i.) to suspect 

 the phlogistic theory of combustion to be wrong, and (II.) to 

 establish the consistent theory of combustion the basis of 

 chemical progress in modern times. Giaber knew the nature 

 of ALCOHOL and GASES, and was thereby the Priestley or 

 Lavoisier of his time. He described the operations of 

 DISTILLATION, FILTRATION, SUBLIMATION (obtained mer- 

 cury by sublimation from cinnabar) ; he described also 



