( 210 ) 



which is fhewn at Jig. 9, and in this figure L M N T, Ihcws that 

 part which, in fig. 2, is reprefented at AB F : and the round hole 

 in that figure is in this fhewn at a b c. In this figure alio O P Q R 

 is the part reprefented in fig. 2, at C D E, and the round hole, d e f , 

 in this figure, is the hole K L M, \nfig. 2. The brals fpring V W X 

 is tliat which, \nfig. 3, is fhewn at A B C D, and the fpring AB C D, 

 in this figure, the fame which is fliewn, in^^. 4, at I K LM. The 

 piece of brafs fliewn in fig. 5, N O P Q R S T, is reprefented in this 

 figure at E F G, and the two fcrews, by which it is made faft, are 

 fliewn at Y and Z ; the brafs fcrew, in fg. 7, marked C D, is in 

 this figure fliewn at H, where it is feen fcrewed in its place. 



I then directed the limner to make a drawing of the entire in- 

 flrument, with the micro fcope joined to it, and the glafs tube in- 

 clofed in it, the fame being adjulled ready for ufe, and fo placed 

 before the view ; this is fliewn at /^ 10, A B C D E F G H ; the 

 filver or brafs plates, inclofing the magnifying glafs, are fliewn at 

 I K LM ; the brafs I'crew, by which the magnifier is fixed, is fliCMai 

 at 2 ; the fcrew, by which the obje6l is placed at a proper diftance, 

 is marked at 3, and the glafs tube, containing the Eel, and fixed iu 

 the inllrument, is reprefented by Q R S T V W X Y. 



It is my practice to ufe glafs tubes of a fize fuitable to the Eels 

 which are to be viewed ; and though but a fmall Eel be placed 

 within the tube with its head towards the bottom, yet the glafs 

 tube will project fo far below the inftrument, that it may be held 

 in the hand by that part, fo that it will not be neceflaiy to touch 

 the inflrument with the hand, and with the other hand the magni- 

 fier, which will be held next the eye, may, by means of the fcrew 

 at 3, be drawn out, or comprefled inwards, until the part of the 

 objeft to be viewed is brought to a proper difl:ance. 



When I wifli to take out or put in the glafs tube, which 1 gene- 

 rally do at the upper end, I remove the magnifier a little on one 

 fide, that it may not be fcratched by the glafs tube ; this pofition 

 or removal is marked in the figure by the dotted line N P F. 



E e 2 



