CONSTRUCTION OF PONDS. 33 



of winter. Analysis shows it to contain carbon- 

 ate of lime, alumina, and iron in small quantities, 

 with a small amount of free carbonic-acid. Pass- 

 ing down a race-way (a) fifty -five feet long, 

 four wide, and six inches deep, the water enters 

 pond No. 1 ; and, following the course of the 

 arrows, passes successively through 1, 2, and 3, 

 and is discharged at the point I into No. 4. This 

 pond is not used for fishes, but for the culture of 

 water-cress, an article which finds a ready sale in 

 the New York market. At the points marked x 

 are sluice-gates, at which are placed screens of 

 wire gauze. These screens are arranged in pairs, 

 and each performs a separate duty the upper 

 arresting all leaves, sticks, or other floating trash 

 which may find its way into the ponds, and the 

 lower preventing the mixture of fishes of different 

 ages. 



When the young fishes are first placed in No. 1, 

 were the whole curront of the stream allowed to 

 pass through they would be washed against the 

 lower screen and perish ; but by means of the cross 

 race (c) the amount of water supply can be regu- 

 lated to a nicety. -The hatching-house (H) for- 

 merly occupied the site of the gold-fish pond (5), 

 and was supplied with water from the spring by 

 pipes, but some two years since was removed to 

 its present and more convenient location. At G 



2* 



