878 BULLETIN OF THE BUREAU OF FISHERIES. 



of solution therefore gradually slows and the concentration in the water treated 

 is constantly falling. If a fixed siphon is used the same difficulty is met. The 

 rate of flow through the siphon depends on the head of the solution, and is 

 therefore never constant. The simplest way to meet this difficulty is the use 

 of a floating siphon, aJid this is an essential part of the method herein described. 

 A siphon made of glass tubing with rubber connections may be mounted upon 

 a wooden frame and the frame built upon a substantial fiOat. The simplest 

 carpentry suffices to adapt it to almost any shape or size of container. (See 

 Fig. I .) The frame holds the siphon in such fashion that one arm hangs outside 

 the container and the other in the solution. The outer arm is made the longer, 

 giving such head as is desired. The inner arm passes through the float, ending 

 flush with its lower surface. The frame carrying the siphon floats on the sur- 

 face of the solution, falling as the level of the latter is lowered. (Fig. 2.) The 

 siphon always has the same relation to this level, and therefore the head is 

 always the same and the flow constant. It is better that the frame be 

 light in weight, relative to the base or float, so that it will float nearly up- 

 right, or else guides must be placed at the top of the container to hold the 

 frame in position. This flow of solution may be delivered to the water flow 

 directly or led to it by troughs or any convenient way. 



DETAILS OF THE CONTINUOUS TREATMENT. 



The metric system is of such great convenience for the measurements and 

 calculations involved that it is used throughout this description, a table for con- 

 version to other units being given. It is worth while to calculate by the metric 

 system, and, if measurements have to be made by other systems, to reduce them 

 to metric units. The reason for this lies both in the advantage of decimal calcu- 

 lation and in the simple relationship of the metric units for weight and volume. 

 For practical purposes i cubic centimeter (c. c.) of water weighs i gram, and i 

 liter (1,000 c. c.) of water i kilogram, 1,000 grams, or i ,000,000 milligrams (mg.). 

 Small metric graduates and rules are easily obtained. Weighing will more com- 

 monly be by avoirdupois, and conversion should be made. Some method of 

 measuring small volumes should be available. A i cubic centimeter volumetric 

 pipette graduated in fifths or tenths is very useful." 



For the actual use of fish culturists or others, the details of methods, pro- 

 cedure, and apparatus necessary to apply copper sulphate continuously to 

 waters containing fish for the elimination of algae or for other purposes, without 

 injury to the fish, are as follows: 



a Such pipettes, marked in tenths of a cubic centimeter, may be obtained for about 25 cents each 

 from Eimer & Amend, 205 Third avenue, New York City; Arthur H. Thomas & Co., Twelfth and Walnut 

 streets, Philadelphia; or Bausch & Lomb Optical Company, Rochester, N. Y. 



