260 PHILOSOPHICAL TRANSACTIONS. [aNNO 1787. 



produce its number in a less time than would probably have been the case if 

 both ovaria had been preserved, is evident from the above recited experiment. 



XXII. Experiments made to determine the Positive and Relative Quantities of 

 Moisture Ahsorhedfrom the Atmosphere by Various Substances, under similar 

 Circumstances. By Sir Benj. Thompson, Knt., F. R' S. p. 240. 

 Having provided a quantity of each of the under-mentioned substances, in a 

 state of perfect' cleanness and purity, says Sir B. T., I exposed them, spread out 

 on clean China-plates, 24 hours in the dry air of a very w^arm room, the last 6 

 hours the heat being kept up to 85° of Fahrenheit's thermometer; after which I 

 entered the room with a very accurate balance, and weighed equal quantities of 

 them, as expressed in the following table. Then each substance being 

 equally spread out on a clean China plate, they were removed into a very 

 large uninhabited room on the 2d floor, where they were exposed 48 hours, on 

 a table placed in the middle of the room, the air of the room being at the tem- 

 perature of 45° F. ; after which they were carefully weighed in the room, and 

 were found to weigh as under-mentioned. 



They were then removed into a very damp cellar, and placed on a table, in 

 the middle of a vault, where the air, which appeared by the hygrometer to be 

 completely saturated with moisture, was at the temperature of 45° p. ; and in 

 this situation they were suffered to remain 3 days and 3 nights, the vault being 

 hung round, during all this time, with wet linen cloths, to render the air as 

 damp as possible, and the door of the vault being shut. At the end of the 3 

 days I entered the vault, with the balance, and weighed the various substances 

 on the spot, when they were found to weigh as is expressed in the 3d column of 

 the following table. 



Weight after Weight ^fter be- Weight after 



The various substances. JfS ^"^^^ ing exposed 48 being exposed 



24 hours in a hours in a cold 72 hours in a 

 hot room. uninhabited room. damp cellar, 



Pts. Pts. Pts. 



Sheep's wool 1000 1084 1 163 



Beaver's fur 1000 1072 1125 



The for of a Russian hare 1000 1065 1115 



Eider down 1000 IO67 1112 



„.„ f Raw, single thread 1000 1057 1 107 



1 Ravelings of white tafFety 1000 1054 1 103 



, . f Fine lint 1000 1046 1 102 



l.inen | Ravelings of fine linen 1000 1044 1082 



Cotton wool 1000 1043 1089 



Silver wire, very fine, gilt, and flatted, 7 ^^^ ,^00 1000 



being the ravelings of gold lace j 



The weight used in these experiments was that of Cologne, the parts or least 



