204 Journal of Agricultural Research vol. xx, No. 3 



On account of the writer's moving from Corvallis, Oreg., to Houston 

 Tex., a few days later, this experiment could not be repeated on Oak 

 Creek, but a similar experimemt was made on a small stream or "bayou" 

 a short distance from Houston. This stream, flowing about 1,500 liters 

 per minute, is sluggish, fairly even in width and depth, and contains 

 water moderately alkaline and rich in lime. The only abundant snail 

 in the stream was a small Ancylus which occurs on dead leaves on the 

 bottom. A few specimens of Physa anatina were obtained at each 

 dredging. 



To treat this stream a 10-gallon barrel was used, fitted with a glass 

 spigot as before but protected from plugging up by the use of a glass 

 funnel with the large end inside the barrel, this being covered with 

 cheesecloth to strain the solution as it flowed out. The addition of a 

 few cubic centimeters of sulphuric acid prevented the flocculent pre- 

 cipitation of iron sulphate, which is present as an impurity in commer- 

 cial copper sulphate. The diminution in rate of flow from the spigot 

 resulting from a lowering of the level of the fluid in the barrel follows a 

 parabolic curve, in this case decreasing fairly steadily from 50 cc. to 

 30 cc. per minute until the barrel was half empty. To prevent a greater 

 fall In pressure a 20-liter jar was placed above the barrel and connected 

 with it by an automatic siphon, so that the contents of the jug would 

 be utilized when the barrel was half empty. A simpler method would 

 have been the utilization of a tube equal to the height of the barrel to 

 give a greater head. By this method the entire contents of the barrel 

 could be utilized before refilling without too great a change in the rate 

 of flow of the copper solution. The experiment was allowed to run for 

 72 hours, although 48 hours' exposure to the copper solution had been 

 found experimentally to be sufficient to kill snails. However, in a 

 flowing stream it was thought advisable to give an extra day to make 

 up for uneven flow and dilution in the deeper portions of the stream 

 during the early part of the experiment and to give time for diffusion 

 into the "dead" water along the sides of the stream. At the end of 

 the experiment — that is, for the last 12 hours — the lower half of the 

 barrel was allowed to run itself out, thus gradually diminishing the 

 strength of the solution in the stream. It was thought that in this 

 way the actual time during which the stream was treated by a full 

 1 to 500,000 solution would be at least 48 hours. Three days after the 

 completion of the experiment the stream was again dredged at intervals 

 of about one-third of a mile at the same points at which dredgings 

 were made prior to the experiment. A few empty Physa shells were 

 found, but no living snails of any kind were obtained at any point 

 along the length of the stream (about 1% miles). It was unfortunate 

 that the stream was not longer so that the actual distance over which 

 the treatment was effective could be determined, but since this would 



