246 Biographical Accmnt of [April, 



air by animals and by combustion is restored. The present experi- 

 ments show that raw silk, cider down, and various similar bodies, 

 may be substituted for the leaves of plants without diminishing the 

 evolution of oxygen gas. The light of lamps was found to produce 

 the same effect as solar light ; but our author did not obtain gas by 

 heat when light was excluded. He confirmed Dr. Priestley's 

 observation, that green-coloured water produces much oxygen gas, 

 but the green matter, according to him, is not of a vegetable 

 nature, but consists of a congeries of animalcules. This subject of 

 the evolution of oxygen gas by exposing various substances under 

 water to the action of the solar rays is not yet cleared up. When 

 our author wrote, chemical analysis was not far enough advanced to 

 enable experimenters to determine exactly the nature of the gases 

 evolved, and modern chemists have not paid any attention to the 

 subject. 



4. Experiments to determine the positive and relative Quantities 

 of Moisture absorbed from the Atmosphere by various Substances 

 under similar Circumstances. Phil. Trans. 1787. P. 240. — The 

 following table exhibits the result of these experiments : — 



5. Experiments on Heat. 

 object of these experiments is 

 various bodies. He surround 

 various bodies inclosing the 

 thermometer was raised near 

 into ice-cold water. The ti 

 degrees was noted, and the 

 versely as this time. The 

 results : — . 



Phil. Trans. 1792. P. 48.— The 

 to determine the conducting power of 

 ed the bulb of a thermometer with 

 bodies and bulb in a glass ball. The 

 y to a boiling heat, and then plunged 

 me of cooling a certain number of 

 conducting power considered as in- 

 following table shows the principal 



