28 DR BREWSTER on the Existence of Two New Fluids 



ed by a very beautiful optical phenomenon. When the fluid has 

 extended itself into a thin plate, it ceases to reflect light, like 

 the most attenuated part of the soap-bubble, and when it is again 

 accumulated into a thicker drop, it is covered with all the co- 

 loured rings of thin plates. When one of the drops of fluid is 

 very minute and perfectly circular, it resembles, in the most ac- 

 curate manner, the small drops which pass from the vacuity, and 

 which have been described in the preceding section. 



After performing these motions, which sometimes last for ten 

 or twelve minutes, the fluid suddenly disappears, and leaves be- 

 hind it a residue of minute and separate particles, which are 

 opaque by reflected, but transparent by transmitted light. 

 Upon examining this residue with a single microscope held 

 in the hand, I was surprised to see it again start into a 

 fluid state, and to extend and contract itself as before. This 

 was owing to the moisture of the hand ; and I can at any time 

 revive the indurated substance, by the approach of a moist body. 

 A portion of the fluid, which I took out of a cavity twenty days 

 ago, is still capable of being restored to a fluid state by mois- 

 ture. This portion was shewn to an eminent naturalist, the 

 Reverend Dr FLEMING of Flisk, who remarked, that, had he ob- 

 served it accidentally, he would have ascribed its apparent vi- 

 tality to the movements of some of the animals of the genus 

 Planaria. 



After the cavity has remained open for one or two days, the 

 second fluid comes out of it, and hardens very speedily into a 

 yellowish resinous-looking substance, which is perfectly transpa- 

 rent. This substance absorbs moisture, but with less avidity 

 than the other. It is not volatilized by heat. It is not soluble 

 in water or alcohol ; but it is rapidly dissolved with efferves- 

 cence by the sulphuric acid. The nitric and muriatic acids also 

 dissolve it. 



