PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 581 



hot. " The liair is first cut short with a knife, the shearer beginning at 

 the head ami following the direction of the fleece toward the tail. The 

 animal is then rubbed in the reverse direction with a sort of brush or comb, 

 which detaches the fine wool from next the skin (the asuli) nearly free 

 from hair. When the animals are «ot shorn, they relieve themselves of 

 these winter vests of delicate down, by rolling on the ground or rubbing 

 against the rocks." Seeing that the original possessors of the asuli are 

 nearly as wild as the winds, materials for thousands of shawls must be 

 annually blown about and utterly wasted amongst the pinnacles and crags 

 of those desolate regions. M. Gerard thinks that at present a very great 

 quantity of the genuine asuli is lost by being mixed with the coarser hair 

 and common wool, and thus indiscriminately manufactured into bushmeena. 



Sewerage. 



The regular discussion was opened by Mr. Woodward, of the firm of 

 Knights & Woodward, of Brooklyn, who exhibited specimens of their 

 hj'draulic cement sewer pipe. Mr Knights followed, and said the pipes 

 were made of cement, gravel and sand, precisely the same as concrete. 

 They are very durable, and being made on polished cores, they are true 

 throughout the whole bore. The p'roportions are two parts of sand and 

 gravel and one of cement ; this is kept damp for seven or eight weeks and 

 made to set very slowl3^ They can be made much cheaper than ordinary 

 clay pipe, and they never get out of shape. The size here exhibited is 

 twelve inches in diameter, and is sold at 50 cents a foot; and that of three- 

 inch bore costs 14 cents a foot. We make some twenty -four inch pipes ; 

 they are made in an egg shape, and sold at $1.30 per foot. These pipes 

 are specifically adapted for distribution and drainage in cities and villages. 

 They will stand the most severe tests, and improve in strength with age and 

 use, and are now extensively adopted by eminent hydraulic engineers. The 

 sewer-pipes are in use in New York, Brooklyn, Central Park, Hartford, &c., 

 and also under heavy railroad embankments. They stand the most severe 

 test of acids. In the city of Brooklyn over forty miles of this pipe is used 

 for the street sewers. 



Mr. Woodward read some extracts from a report of an English commis 

 sion appointed to examine the sewerage of London, showing that in their 

 opinion small pipes are less likely to be obstructed than large sewers wiiiel- 

 are several times more expensive. 



Mr. Enos Stevens gave the results of some experiments he had tried t( 

 find the descent required for water to carry along stones and other sub 

 stances. The conclusion was that in a V shaped trough, after it has 

 become smooth, a descent of one foot in fifty-eight feet of length was suffi- 

 cient to wash away all obstructions. 



City Sewerage. 



The following paper was presented by ^fr. Samuel McEIroy, C. E., o/ 

 Brooklyn : 



The attention of the Polytechnic Association, which is directed to th« 

 various public and scientific improvements of the age, and to the various 



