'6 Proceedings of the Royal Physical Society. 



having their constituents purified, be changed into gold and 

 silver. What an amount of fruitless labour the holding and 

 promulgation of this unfortunate opinion may have caused, 

 it is difficult to conceive. Besides the metals just named, 

 Geber was acquainted with some of the salts of the alkalies, 

 and succeeded in carrying out an operation, an extension of 

 which forms one of the great chemical industries of the 

 present day, viz., the conversion of the carbonates of the 

 alkalies, or at all events, the conversion of one of these, 

 carbonate of soda, into caustic soda, by boiling a solution of 

 the carbonate with quicklime. He also succeeded in prepar- 

 ing nitric acid, although by a somewhat tedious process, and 

 from the nitric acid he obtained aq^ua regia, which, we are 

 told, he used for dissolving gold. Other compounds with 

 which we work every day he was also possessed of, one of 

 which was the famous red precipitate, or oxide of mercury, 

 which Dr Priestley used nearly a thousand years after in his 

 celebrated experiment, in which he prepared oxygen gas for 

 the first time, and which therefore has always, since that 

 experiment was made, been invested with a peculiar interest 

 to students of chemistry. There can be little, indeed almost 

 no doubt, that Geber obtained many of the processes he 

 described from some previous worker in the same field, but 

 still he is entitled to all praise as being a patient and ap- 

 parently an enthusiastic investigator. He was, of course, 

 completely on the wrong track when he employed his time 

 and talents in the almost childish and absurd work of searching 

 for the means of transforming the baser metals into gold and 

 silver ; but while we are inclined to regard with feelings of 

 pity not unmixed with contempt the spectacle of a man 

 devoting his life to such a pursuit, we must not forget that 

 while Geber thus plodded on in murky darkness, he obtained 

 some really useful results, and practised processes so service- 

 able, that they were employed by his successors for centuries 

 after his death. 



Passing from the time of Geber over a period of three 

 or four centuries, during which interval the schools and other 

 educational institutions of Arabia showed their power and 

 value by giving to the world some eminent men, but which 



