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the fin which was to be examined ; but, with all my care, I found 

 that, in doing this, I either impeded the circulation or injured the 

 iin ; I therefore adopted this method : to take Eels about the 

 Hze of one's finger, and let them fwim about in the water for a 

 time, till they were at reft, and then examine their tail fins while 

 in the water, for in that fituation they fpread out their tails, but 

 when taken out of the water, the veiy extremity of the fin gathers 

 up in wrinkles. ' 



In order to impart this pleafing fight to others, I invented and 

 compleated fome inftruments, whereby I exhibited the fame to fe- 

 veral gentlemen of eminence in this country, who all declared, 

 that they did not think any more delightful fpeclacle, nor more 

 worthy of obfervation could be lliewn. 



I have determined to give drawings of the inftruments by which 

 I exhibited this circulation of the blood, and by which thofe who 

 defire to view the fame may be eafily gratified. 



I firft prepare a piece of brafs about half the thicknefs of the 

 back of a common knife, and of the fhape reprefented at fig. 2, 

 A B C D E F ; this I hammer upon an anvil fome time, to make 

 it the tougher, and make two large holes in it, as fliewn at G H I 

 and K L M. I alfo drill fix fmaller holes at P Q R S and NO. I 

 then bend this piece of brafs at the end A B F, and at the dotted 

 line B F, fo that it may form a right angle with the other part, and 

 alfo bend the other end C D E, in like manner. 



I then take another flat piece of brafs of the fame thicknefs, 

 which, being well hammered, will anfwer the purpofc of a fpring ; 

 this is reprefented ^tjlg. 3, A B C D, and I haminer it into feme- 

 thing of a hollow fliape, and file in the lower end of it a cavity, 

 in order that it may in part furround the glafs tube I flaall hereafter 

 defcribe ; this round cavity is fliewn at AD. I then drill four 

 holes in it at E F G H, to correfpond with thofe marked P Q R S in 

 fg. 2 ; and with brafs rivets I join the two pieces together. I 

 then prepare another brafs fpring, as at Jig. 4, I K L M, in which 



Vol. II, E c 



