468 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



the sewers in the cities and larger towns has, of late, greatly 

 increased. The following extract from the committee's re- 

 port deals very fully with the subject in hand, while at the 

 same time it manifests the gravity which the members at- 

 tach to the matter: "The committee made a special inves- 

 tigjation into the sew^eras^e arrans^ements of the town of Cam- 

 bridge, where water-closets are general, though not univer- 

 sal. The outlets of all the sewers were found to be under 

 the level of the surface water in the River Cam, so that the 

 sewerage is backed up into the sewers for a considerable 

 distance, and the subsoil is constantly saturated with both 

 water and sewerage in the lowest parts of the town. As 

 many of the sewers are old and of irregular shape, much 

 escape of the sewerage into the subsoil must take place. 

 Inquiries were made into the state of some of the water-wells 

 belonging to private houses, and it was found they were all 

 contaminated by sewerage, owing to their proximity to the 

 sewers in the streets and to the drains on the premises, so 

 that the water can not be used for drinking, but only for 

 w^ashing. The chief general importance of the inquiry into 

 the condition of Cambridge is the proof thus obtained of the 

 contamination of wells, and therefore of subsoil, by the 

 agency of pervious street or house sewers constructed in 

 their vicinity ; and the sub-committee gave expression to 

 the conviction forced upon it in the course of its inquiries 

 that all sewers, properly so called (that is to say, drains into 

 which the refuse from human habitations is admitted), 

 ought to be constructed of materials which are altogether 

 impervious, and that a separate system of pervious drains, 

 similar to agricultural drains, should be constructed where 

 necessary to dry the subsoil. The sub-committee is of the 

 opinion that the further construction of pervious sewers 

 should be prohibited by Parliamentary enactment." 



A NEW DRY-DOCK. 



To meet the exigencies of an increasing coastwise and for- 

 eign commerce at the port of Philadelphia, a new dry-dock 

 has lately been completed by the Messrs. Cramp & Sons, build- 

 ers of the American line of steamships. The location of this 

 structure, the w^ant of which has of late been severely felt, 

 is on the site of their present marine railway on the Delaware 



