J 



THE 1'HOGHtSS OF 



volves round the surface of an excited body in 

 i spiral direction. Doubtless the magnetic poles 

 jf the earth result from electric currents. But 

 we are still in the dark with respect to the reason 

 why only steel, nickel, ami cobalt can be con- 

 verted into magnetic needles, and why the mag- 

 netic virtue is so weak in the oilier metals. 



CHEMISTRY. 



CHKMISTRT, unlike the other sciences, sprang 

 originally from delusion and superstition, and 

 was, at its commencement, on a level with magic 

 and astrology. After shaking off this unhallowed 

 connection, it offered its services to the physician 

 in ilit; humble rank of an assistant in the pre- 

 paration of medicines. Its services being ac- 

 cepted, it ventured occasionally to investigate the 

 nature of the medicines employed by medical 

 men, to simplify and improve them, and even to 

 suggest the employment of new remedies, when 

 they appeared from the researches made to be 

 superior to the old. From this humble begin- 

 ning, it gradually extended its benefits to miners, 

 metallurgists, and artists in general ; and examin- 

 ing the properties of all the substances in nature, 

 ameliorated, and improved, and simplified many 

 of the most useful processes. 



We have no evidence that the ancients were 

 acquainted with chemistry, in the modern sense 

 of^he word ; but it was cultivated by the Arabians, 

 after the establishment of the empire of the 

 caliphs. Geber, who lived in the eighth cen- 

 tury, is almost the only chemical writer among 

 the Arabians whose works have become known 

 in Europe. Four tracts of his, known by the 

 quaint titles, " Of the Investigation or Search of 

 Perfection ;" " Of the Sum of Perfection, or the 

 Perfect Magistery ;'' "Of the Invention of Verity 

 or Perfection ;" " Of Furnaces," &c., have been 

 translated into Latin, and likewise into English. 



His object was the preparation of a universal 

 medicine ; and during his investigation of it, he 

 states a number of circumstances, which enable 

 us to appreciate the degree of chemical know- 

 ledge which he possessed, and which may be 

 summed up under the following heads. 



1. He was acquainted with gold, silver, cop- 

 per, iron, tin, lead, mercury, arsenic. Whether 

 he was acquainted with antimony is not so clear. 



2. Potash and soda were known to him, at 

 least in the state of carbonates. But whether he 

 was aware of their different properties does not 

 appear. 



3. He was acquainted with sulphuric acid, 

 nitric acid, and, probably, muriatic acid ; or at 

 least he prepared an aqua regia, by mixing sal 



ammoniac with nitric acid, which enabled him to 

 form a liquid capable of dissolving gold. 



4. He knew common salt, saltpetre, sal nm- 

 moniac, alum, sulphate of iron, borax, corrosive 

 sublimate. 



5. He was acquainted with red oxide of mer- 

 cury, oxide of copper, red lead and litharge. 



6. He employed vessels for distillation, and 

 used aludels of stoneware, glass, and metal. Tlio 

 water bath, the common still, the method of dis- 

 tilling per descensum, furnaces for melting and 

 calcining metals were familiar to him. -Vinegar 

 was used as a solvent by him in many of his 

 processes. 



As chemistry is entirely an experimental 

 science, and as the number of I. ids and com- 

 pounds gradually discovered is exceedingly great, 

 it would be impossible, in a sketch of this kind, 

 to notice every individual improvement or dis- 

 covery. We shall, therefore, satisfy ourselves 

 with pointing out those which had the greatest 

 influence upon the progress of the science. 



When we have a compound of two bodies 

 united together, and wish to separate one of 

 them, the successful process is to add a third 

 body. This third body, in many cases, unites 

 with one of the ingredients of the compound, 

 and disengages the other. Thus saltpetre is a 

 compound of nitric acid and potash, in the pro- 

 portion of 6 -75 of the former, and six of the 

 latter. If we want to procure the nitric acid, 

 we shall succeed if we put 12-75 of nitre into a 

 retort, and pour over it 12*25 of the sulphuric- 

 acid of commerce. Upon applying heat to this 

 mixture, the nitric acid of the saltpetre will come 

 over into the receiver, together with the water of 

 the sulphuric acid, making together nine ; and 

 there will remain in the retort all the potash, 

 combined with all the sulphuric acid, weighing 

 together sixteen. Magor, in the 14th section of 

 his treatise Le Spiritu nitro-aereo, published in 

 1678, seems to have been the first person who 

 explained in an intelligible manner, these mutual 

 unions and decompositions which take place in 

 salts when a third body is judiciously added. 

 The theory was afterwards suggested by fc-ir 

 Isaac Newton at the end of his Optics. The 

 union he ascribed to an attraction existing be- 

 tween the atoms of bodies, and the decomposition 

 to the addition of a body having a greater attrac- 

 tion for one of the constituents of the compound 

 than the constituent has which it displaces. 

 Tables exhibiting the order in which these de- 

 compositions take place, were first drawn up by 

 Geoffroy Junior, in 1718. These tables were 

 gradually improved, till at last they were brought 

 to the greatest degree of perfection which they 

 have yet attained, by Bergmann, in the year 

 1 7 S3. 



