( 220 ) 



I alfo made another inftrument of like Hiape with the former, in 

 wliich the fpring reprefented in^^. 9, at ABCD, is a little fliortcr ; 

 and to this I fcrewed the brafs containing the magnifying glafs, as 

 reprefented in fig. 11, H I K L, on which magnitier or microfcope, 

 I fixed a little dith or concave reflc6lor, to throw more light on the 

 ohje6l ; to which intent I filed away as much as I could of the brafs 

 about the microfcope, as may be feen at Jig 12, MN O P, where 

 this is lliewn on the oppofite fide. 



I have alfo given a drawing of the glafs tube containing the Eel, 

 which is fhewn ^tfig. 13, Q R S T V. The Eel placed in this tube, 

 I at firfi; ufcd to cover entirely with water, but I found that when 

 the tail was left out of the water it would, being wet, fprcad itfelf 

 on the glafs, and be more eafily viewed (this fin of the tail is Ihewn 

 at W) ; and I always, before putting in the Eel, wetted the infide of 

 the glafs, for otherwife the glutinous matter from its body would ad- 

 here to the dry glafs and impede the view. 



I alfo recommend to thofe who make thefe experiments, as 

 foon as ever the Eel is taken out of the tube, to let the glafs be 

 well cleaned, for otherwife the glutinous matter from the fith will 

 dry on the glafs. 



I have caufed many glafs tubes to be blown for thefe experi- 

 ments, but the rounder they are, and the thinner the glafs, the bet- 

 ter : fome of them I caufed to be made clofed at one end, as here 

 fhewn at Q, others I clofed with a cork. 



I have alfo viewed the circulation of the blood in the tail fin of a 

 Perch, and that in fuch minute veflels as would only admit one glo- 

 bule or particle of blood to pafs through at a time. 



I once faw in a large artery in a Perch, (I call it large in refped; 

 of the mofi; minute ones, though this was not thicker than an hair 

 of one's head), and which is reprefented at ^g-. 14, the blood pro- 

 truded from A to B, though but faintly ; from B to C, I could only 

 perceive a fmall agitation of the blood, and beyond C it was coagu- 

 lated : from this artery there arofe a branch as reprefented in the 



