INVESTIGATION OF RIVERS AND LAKES. 71 



their meaning. We believe it is nmch better to be content for the present with the 

 observation and recording of tacts, and wait until more facts are in before interpreting 

 their meaning. 



As indicating the character and scope of the held work which we have been doing 

 in this line, I shall give the substance of the directions or suggestions which have been 

 furnished for the guidance of the various parties which the Commission has had 

 engaged upon this work. During the last year or two there have been several volun- 

 teer observers, and during the present summer six parties were engaged upon field 

 work in accordance with this plan. 



Separate outlines were prepared for those parties engaged in lake study and those 

 studying rivers, but in this connection it will be sufficient to give but one of the 

 outlines. 



The outline for lake study will serve our purpose, and I give it essentially as it was 

 sent to the field parties, without taking time to put it in better form for this paper, as 

 I perhaps should have done. 



In the study of any lake attention should be given to the following : 



OUTLINE FOR LAKE STUDY. 



PHYSICAL FEATURES. 



Geographic position : 



size: Form; greatest length and width and the direction of each; length of shore line. 

 Depth: Maximum and average; soundings should be made in many different places and the con- 

 figuration of the bottom determined as accurately as possible. 



Temperature: Determine the bottom temperature in various places; also at different depths, say at 

 intervals of 10 feet. At what depth does the temperature of the air cease to affect that of the 

 water* Or, in other words, at what depth does the temperature remain constant? These 

 observations should be repeated once a week if possible and should extend through at least 

 one year. The temperature of the air should also be taken, at the same time. 



Ice: When and where does the lake begin to freeze, in what direction does the ice spread most rapidly, 

 and when does the lake become frozen over > What places remain unfrozen and what is the 

 cause? Note the thickness and character of the ice from time to time; when and where is 

 the maximum thickness reached? Depth of snow covering ice from time to time. When and 

 where does the ice begin to melt in spring, how and in what direction does it progress, and 

 when does the ice finally break up? Upon what shore and to what extent is it piled up? Is 

 there any regularity in the formation of ice-cracks in different parts of the lake? 



Purity: Character of the water, whether clean or muddy, hard or soft; sources and extent of contam- 

 ination. 



Bottom: Whether of sand, gravel, bedrock, or mud, and character in different places. Determine 

 depth of bottom deposit if possible. 



Shores: Whether high or low; dry, marshy, or muddy; and of what material made up, as mud, sand, 

 gravel, clay, or rock; geologic age to which outcropping rocks belong; depth and character of 

 drift, if any, in the immediate vicinity of the lake. This can be determined by learning the 

 depth at which bed-rock is struck in the wells of the neighborhood. How do you explain 

 the origin of the lake ? 



Inlet: What streams flowing into the lake and the amount of water carried by them; temperature, 

 purity, and general character of the water. Locate and note the character of all springs con- 

 nected with the lake, not omitting any that may be in the lake's bottom. 



Outlet: What the outlet is, into what it flows; character as to size, rate of current, and volume of 

 water discharged per minute. Compare amount of inflow with outflow, and make investiga- 

 tions for the purpose of determining the amount of evaporation which takes place from the 

 surface of the lake during each month. This may be approximated by evaporating, in the 

 open air, the water in a large, shallow pan. This, of course, would ueed frequent repetition. 



