256 PHILOSOPHICAL TRANSACTIONS. [aNNO 178/. 



the darkest of them: nor did I perceive any similar phaenomena last lunation, 

 though I then viewed the same places with the same instrument. 



The appearance of what I have called the actual fire or eruption of a volcano, 

 exactly resembled a small piece of burning charcoal, when it is covered by a very 

 thin coat of white ashes, which frequently adhere to it when it has been some 

 time ignited; and it had a degree of brightness, about as strong as that with 

 which such a coal would be seen to glow in faint daylight. All the adjacent 

 parts of the volcanic mountain seemed to be faintly illuminated by the eruption, 

 and were gradually more obscure as they lay at a greater distance from the crater. 

 This eruption resembled much that which T saw on the 4th of May, in the year 

 1783 ; an account of which, with many remarkable particulars relating to volcanic 

 mountains in the moon, I shall take an early opportunity of communicating to 

 this society. It differed however considerably in magnitude and brightness; for 

 the volcano of the year 1783^ though much brighter than that which is now 

 burning, was not nearly so large in the dimensions of its eruption : The former 

 seen in the telescope resembled a star of the 4th magnitude as it appears to the 

 natural eye; this, on the contrary, shows a visible disk of luminous matter, very 

 different from the sparkling brightness of star-light. 



p. s. M. Mechain having favoured me with an account of the discovery of his 

 comet, I looked for it among the Pleiades, supposing its track since the 10th 

 of this month to lie that way; and saw it April igth, at lO*" 10™ sidereal time, 

 when it preceded Fl. d Pleiadum about 54' in time, with nearly the same de- 

 clination as that star; but no great accuracy was attempted in the determination 

 of its place. As I have mentioned the comet in a foregoing paragraph of this 

 paper, I thought it proper here to add my observation of it. " The comet is 

 nearly round, with a small tail towards the north following part ; the chevelure 

 extends to about 4 or 5'; and it has a central, very small, ill-defined nucleus, 

 of no great brightness." 



XXL An Experiment to determine the Effect of Extirpating one Ovarium, on 

 the number of young produced. By John Hunter, Esq., F.R.S. p. 233. 

 In all animals of distinct sex (says Mr. H.) the females, those of the bird kind 

 excepted, have, I believe, 2 ovaria, and of course the oviducts are in pairs. By 

 distinct sex I mean when the parts destined to the purposes of generation are 

 of 2 kinds, each kind appropriated to an individual of each species, distinguished 

 by the appellation of male and female, and equally necessary to the propagation 

 of the animal; the testicles, with their appendages, constituting the male; 

 the ovaria, and their appendages, the female sex. 



As the ovaria are the organs which, on the part of the female, furnish what 

 is necessary towards the production of the 3d, or young animal ; and as females 



