VOL. XXXI.J PHILOSOPHICAL TRANSACTIONS. 523 



caps of niaintenance, I at first fixed a plain glass before the sight, but soon 

 found that the vapour of the breath would make such a dew on the surface of 

 the glass, that it hindered its transparency; to remedy which, I found it neces- 

 sary to prolong that side of the cap that was before the eyes, and thereby en- 

 large the prospect of what was beneath. 



An Account of an Aurora Borealis, observed at Dublin, Feb. 6, 172O-I. 



By J, W. N«368, p. 180. 



A Description of an Aurora Borealis^ seen on the same Day at Cruwys-More- 

 hardf in Devonshire. By Samuel Cruwys, Esq. F. R. S. N'' 368, p. 1 86. 



These two descriptions of the aurora borealis being of the most ordinary 

 kind, as frequently seen, are of no use to be here retained on the present 

 occasion. 



Observations on the Muscular Fibres of Fish. By Mr. Leuwenhoeck, F, R. S. 



W 368, p. 190. 



It has been asserted that nature, in all her various productions, constantly 

 observes the same course and manner of operation. To this assertion my obser- 

 vations by no means agree, neither those that I have made on the generation 

 of animals, and the seeds of plants; nor yet those on the muscles and mus- 

 cular fibres of different animals, for the muscles of fishes are not provided 

 with any tendons. 



After the late discoveries I had made of the small vessels in the muscular 

 fibres of the whale, the ox, the sheep, and the mouse, I was apt to imagine, 

 that the same fabric would hold in the muscular fibres of fish likewise ; but as 

 this could not be certainly concluded, I cut a piece of cod fish into small slices, 

 some according to the length of the fibres, and others directly across them, 

 and found, that when I had cut the fibres dexterously through, there appeared 

 in the microscope as great a number of small vessels running along these fibres, 

 as I had formerly seen in the muscular fibres of a whale. 



But what appeared to me the most remarkable was, that in a great number 

 of fibres, in which I was not able to discover any vessels running lengthwise, I 

 observed abundance of small vessels, which seemed to proceed from the mem- 

 branes encompassing the fibres. For in one fibre these vessels appeared to 

 come out of the circumference, or circular tunicle of the fibre, and to pass on 

 to the opposite part of the tunicle; and in another fibre cut transversely, I saw 

 vessels arising from the circumference, and dividing into smaller branches about 

 the middle of the fibre; all which, as far as I could perceive, ended again in 



3x2 



