24 PEACTICAL TREATISE ON 



of the microscope, and in discoveries made by its agency; 

 we have amongst the former, the results of the labours 

 of Adams, Martin, Baker, and Dellebarre ; and amongst the 

 latter, the works of Trembley, Ellis, Baker, Adams, HiU, 

 Swammerdam, Lyonet, Needham, and Withering. Every 

 optician, says Adams,* now exercised his talents in improving 

 (as he called it) the microscope ; in other words, in varying 

 its construction, and rendering it different from that sold by 

 his neighbour. The principal object seemed to be only to 

 subdivide it and make it he in as small a compass as possible, 

 by which means they not only rendered it complex and 

 troublesome to manage, but lost sight also of the extensive' 

 field, great light, and other excellent properties of the more 

 ancient instruments. In 1770, Dr. HiQ published a treatise, 

 entitled The Construction of Timber explained by the Micro- 

 scope, in which not only were the nature and oflSce of its 

 several parts pointed out, but the way of judging from the 

 structure the uses to which the different kinds could be best 

 applied. This work created a great sensation at the time, and 

 revived the ardour for microscopic pursuits. Adams at this 

 period invented a machine for cutting transverse sections of 

 wood so thin, that they might readily be examined by the 

 microscope. This instrument was subsequently improved on 

 by Mr. Gumming, and with it very beautiful sections were 

 made by Mr. Custance, some of which stand unrivalled even at 

 the present day. In 1771, a new edition of the Micrographia 

 Illustrata of Adams appeared, in which he described a lucernal 

 microscope of his own invention; this was subsequently im- 

 proved by his son, George Adams, in 1774, and served to 

 exhibit opaque as well as transparent objects. The solar 

 microscope, too, at this time had been greatly improved by 

 Benjamin Martin, and was made capable of showing on a 

 screen a magnified image of the surfaces of opaque objects. 



In 1787, the Microscopical Essays of the younger Adams 



were published, in which were described aU the instruments 



at that time in use. Of the single form, we have Wilson's, 



shown at fig. 8 ; those of EUis, and Lyonet ; also that of 



* Microscopical Essays, p. 19. 



