860 



drawn in a practical point of view, from his present and previous 

 inquiries as to the use of lead for conveying water : — 



1. Lead-pipes ought not to be used for the purpose of conveying 

 water, at least where the distance is considerable, without a careful 

 chemical examination of the water to be transmitted. 



2. The risk of a dangerous impregnation with lead is greatest in 

 the instance of the purest waters. 



3. Water, which tarnishes polished lead, when left at rest upon 

 it in a glass vessel for a few hours, cannot be safely transmitted 

 through lead-pipes without certain precautions. 



4. Water, which contains less than about an 8000th of salts in 

 solution, cannot be safely conducted in lead-pipes, without certain 

 pi'ecautions. 



5. Even this proportion will prove insufficient to pi'event corro- 

 sion, unless a considerable part of the saline matter consist of carbo- 

 nates and sulphates, especially the former. 



6. So large a proportion as a 4000th, probably even a consider- 

 ably larger proportion, will be insufficient, if the salts in solution be 

 in a great measure muriates. 



7. In all cases, even though the composition of the water seems 

 to bring it within the conditions of safety now stated, an attentive 

 examination should be made of the water, after it has been running 

 for a few days through the pipes. For it is not improbable, that 

 other circumstances, besides those hitherto ascertained, may modify 

 the preventive influence of the neutral salts. 



8. When the water is judged to be of a kind which is likely to 

 attack lead-pipes, or when it actually flows through them impreg- 

 nated with lead, a remedy may be found, either in leaving the pipes 

 full of the water, and at rest for three or four months, or by substi- 

 tuting for the water a weak solution of phosphate of soda, in the 

 proportion of about a 25,000th pai't. 



The following Donations were presented to the Society since 

 last Meeting. 



Proceedings of the American Philosophical Society. Vol. ii. No. 19. 



— By the Society. 

 Laws, Regulations, and Annual Report of the Leeds Philosophical 



Society for 1840-41. — Bi/ the Society. 

 Journal of the Asiatic Society of Bengal, 1841. Nos. 112, 113, 



and 114.— By the Society. 



