Lead pipes ought not to be used for the purpose of conducting water, at least where the distance is considerable, without a careful examination of the water to be transmitted.

2. The risk of a dangerous impregnation with lead is greatest in the instance o f the purest waters.

3. Water, which tarnishes polished lead when left at rest upon it in a glass vessel

for a few hours, cannot safely be transmitted through lead-pipes without certain precautions ; and conversely, it is probable, that if lead remain untarnished, or

nearly so, for 24 hours in a glass of water, the water may be safely conducted through lead-pipes. 4. Water which contains less than about an 8000th of salts in solution, can not be safely conducted in lead pipes without certain precautions. 5. Even this proportion will prove insufficient to prevent corrosion, unless a

considerable part of the saline matter consists of carbonates and sulphates, especially the former.

6. So large a proportion as a 4000th part, probably even a considerably larger proportion, will be insufficient, if. the salts in solution be in a great measure muriates.

7. In all cases careful examination should be made of the water after

it has been running a few days through the pipes; for it is not improbable that other circumstances, besides those hitherto ascertained, may regulate the preventive influence of the neutral salts.

8. Where the water is of sufficient purity to act on lead, a remedy may b e found, either, in leaving the pipes full of water and at rest for three or four months