THE MICROSCOPE. 23 



are told that Benjamin Martin greatly improved the micro- 

 scope of Cuff before described, by the addition of a joint, so 

 that the compound body might be inclined to any angle, and 

 also by the setting of all the lenses in a circular disc of brass, 

 which was capable of being revolved in such a manner, that 

 each lens in succession might be brought under the com- 

 pound body ; this did away with the necessity of screwing and 

 unscrewing when the powers were required to be changed. 

 The compound body could be removed from the lenses, and 

 the lenses themselves then constituted it a single microscope, 

 the arm which supported them was capable of being moved 

 backwards and forwards by means of a rack and pinion, a 

 plan now in use. 



In the year 1746, a philosophical instrument maker of 

 some eminence, named George Adams, published a quarto 

 work, entitled Micrographia Illustrata; or, the Knowledge of 

 the Microscope Explained. In this work were contained a 

 description of the nature, uses, and magnifying powers of 

 microscopes in general, together with full directions how to 

 prepare, apply, and examine, as well as preserve, all sorts 

 of minute objects. This work was the first of the kind 

 published in this country, and contributed not a little to 

 the advancement of microscopic science. The microscopes 

 made by Adams were of two kinds, the single and the 

 compound ; their chief peculiarity consisted in the arrange- 

 ment of the lenses, which were six in number, and were all 

 set in a large plate of brass, capable of being turned upon 

 the central piUar of the instrument, and each lens in suc- 

 cession could be brought underneath a hollowed plate or cup, 

 which served as an eye-piece. For the coarse adjustment, the 

 plate was made to sMe up and down the pillar, whilst for 

 the fine a screw was used, which slowly raised or depressed 

 that portion of the pillar to which the stage was attached. 

 Besides these microscopes of his own invention, we find that 

 he was in the habit of making those of Wilson, Lieberkuhn, 

 and Culpeper, aU of which are fuUy described in the work 

 above-named. 



We have now entered on a period, fertile both in alterations 



