ARABIAN AND MEDIAEVAL SCIENCE. 75 



had done before, and he was in Europe the first to calculate a table of 

 tangents, in which he gave the numerical value for every degree of the 

 quadrant. He also extended the table of sines calculated by Purbacb 

 to every minute of the quadrant, and referred them to a radius of 

 1,000,000 parts, an arrangement which has been found so convenient 

 that it has remained in use to the present day. 



One of the earliest and most zealous cultivators of astronomy by 

 observation was certainly BERNARD WALTHER, a rich citizen of Nurem- 

 berg, and his observations are the more interesting from having been 

 made with clocks regulated by wheels. Walther, who was unacquainted, 

 in all probability, with the writings of Alhazen, was the first modern, 

 astronomer to remark the effects of atmospheric refraction. He seems, 

 however, not to have understood its true principle, for he regards it as 

 affecting the apparent place of a star only when near the horizon. 



Throughout the Middle Ages the alchemists attract our attention as 

 the representatives of the more modern race of chemists. The period 

 from the thirteenth to the sixteenth century was the golden age of 

 alchemy, which was then eagerly pursued by ecclesiastics as well as 

 others, and could reckon among its adepts bishops and kings and 

 even a pope ! The pursuit of the two grand objects of alchemy the 

 transmutation of the common metals into gold, and the discovery of 

 the universal elixir became with many a passion to which time r 

 money, and health were prodigally sacrificed. Disappointment and 

 failure could not damp the ardour of the alchemist, nor could poverty 

 force him from the pursuit of his illusory objects. His faith in his 

 ultimate success sometimes carried him on to persevere in his labours, 

 even at the cost of his life. Indeed, this wonderful perseverance and 

 sublime patience are the most striking characteristics of the alchemists. 

 Perhaps any object less fascinating or glorious than the discovery of 

 the philosopher's stone and the elixir of life would not have induced 

 men to spend their lives in laborious experiments. It was doubtless 

 through these alchemical experiments that truths were acquired which 

 might for ages have remained unknown. The alchemists made innu- 

 merable experiments with metals, and with sulphur, nitre, etc., by which 

 they succeeded in obtaining, not the object of their search, but a 

 knowledge of many important and valuable properties of various sub- 

 stances. It may perhaps appear to the reader a matter for surprise 

 that alchemy should have been by so many eagerly pursued for so 

 many ages, and result in discoveries so few in comparison with those 

 which a single generation of modem chemists may bring to light. The 

 illusory nature of the objects pursued by the alchemists must, how- 

 ever, be borne in mind, and also the fact that the true methods of 

 chemical science had yet to be discovered. There was always a great 

 amount of mysticism mixed up with alchemy, and this was especially 

 the case in those ages when the notion of the supernatural predomi- 

 nated in men's minds. 



