88 PROCEEDINGS OF THE AMERICAN ACADEMY 



tains a very considerable quantity of lead. In the experiments of the 

 preceding tables, the tubes intended to receive the bars were previously 

 filled, and thus the transfer of the bar from one tube to another occu- 

 pied scarcely a second of time. Even this short period was doubtless 

 adequate to provide for some of the oxidation which the bar experi- 

 enced.* Important as the office of air is, it is not adequate of itself to 

 oxidate lead. A bar of lead scraped bright and placed in a desiccator 

 over sulphuric acid remained undimmed for weeks, — during the whole 

 time of the experiment. 



" Influence of Light and Organized Substances in Water. — It is a 

 familiar fact, that well-water recently drawn and exposed to the light 

 and warmth a short time loses much of its air, and becomes insipid. 

 Count Rumford has made this fact the foundation of an important inves- 

 tigation. His conclusions in relation to the joint effect of sunlight and 

 solid miscible, but insoluble, substances in expelling the air from waters, 

 and thus showing a difference between lake, river, pond, and reservoir 

 waters, which are exposed to sunlight, and well or spring waters, which 

 are concealed from it, are of great importance in this connection. t I 

 have made numerous experiments upon this subjeci, which, although 

 still incomplete, taken in connection with the results of Count Rumford, 

 go to establish the following positions : — 



" 1st. Well waters contain more air in solution than lake, river, and 

 pond waters, as a class. 2d. Sunlight and heat falling upon water con- 

 taining solid insoluble substances, organic tissues, or pulverulent mat- 

 ter, expel a portion of the gases. 3d. The germs of animalculaj being 



* I see, in the time between the emptying and filling of leaden pipes employed 

 in experimenting, the explanation of much of the discrepancy between the results 

 of different experimenters. If to this be added the unequal exposures to warmth 

 and light which have been permitted by those engaged in experimenting, I am 

 persuaded that most of the differences in results will be fully accounted for. 



1 He exposed spring water, containing, in a series of experiments, weigiied quan- 

 tities of raw silic, poplar cotton, sheep's wool, eider-down, liare's fur, cotton-wool, 

 ravellings of linen, and Confervae (hair-weed), to the sun's rays, and observed tiie 

 quantity of air disengaged by each substance. It amounted in some cases to one 

 eiglUh of the volume of water. Philosophical Papers, by Benjamin, Count Rum- 

 ford, London, 1802, Vol. I., pp. 218-263. 



The observations of Wohler in 1843 (Jinn, der Chem. und Pharm., Bd. XLI., 

 S. 121), and of Schultz in 1845 (Journ.fur Prakt. Chem., Bd. XXXIV., S. 61-63, 

 ]81;)), upon the evolution of oxygen from waters containing animalculaj and 'green 

 plants,' under the influence of sunlight, were confirmations of some of the experi- 

 uiunlal results of Count lluuifbrd. 



