242 Tlnrl;/-s!.rll, Aiuninl Mrrling 



life to h.-ilch and i-rar youii^- lisli. I lliiiik that is really a vci'v 

 valuable ])()iiit to he considered in eoiiiieetiou with this imcsli- 

 gation. 



Tresideiit : 'J'liat can verv readily he (h'lenniiied. Of eoui'se 

 if you are willing' to take the surface watei-. that is all ri.dit. 



]\Ir. Titeoinh: 'I'liat is usuallv too wai'in. 



President: If you want the deeper water, you will have to 

 consider several (juestions. If you want a \cit larvae supply, 

 yon will have to consider the question as to whetlier there is 

 sufficient water in thi' lake to iiive you water of that teni])erature, 

 because yon will find that the supply of water in the lower ])art 

 of the lake is in ordinary cases extremely small. We have done a 

 great deal of work on lake temperatures, which I ]io])e 

 to have ]ud)lished (hu'ing tlu' year. Now, we find that there 

 are very few lakes indeed wdiere the bottom temperature during 

 the winter rises to an appreciable extent in a way which can he 

 attributed to ground water. This means that very little water 

 is getting into the lake from the ground, since the lake tempera- 

 ture goes down to 2° or 3° C, and the temperature of the 

 ground water in our latitude is somewhere about 8° C. Almost 

 all water coming into tlie lake, comes in the upper ])art above 

 the water level, or immediately below it, and the idea which so 

 many people have that there are great springs down in the bot- 

 tom of lakes is entirely erroneous. In an open sand region, where 

 there is comparatively little clay near the lakes, there may he the 

 same kind of slow circulation through that sand bottom that 

 there is through the general water-bearing strata of the country, 

 l)ut in most lakes the bottom is covered with a very impermea])le 

 layer of mud. We were woi'king on the winter temperatures of 

 Lake Mendota last winter. We had a pipe about twelve feet 

 long, and drove it down into the mud in sixty or seventy feet of 

 water, so that we got a sect;(ui of mud ; we could not get more 

 than five feet of mud to come u]i in tlu' pipe: that was just as 

 sticky as hasty ])udding. There was jiractically no seejiage of 

 water through it: so that the entrance of water into the dee])er 

 part of the lake is slight. It you wanted a small su])ply for a 

 hatching trough, that would be all right; — but if you wanted 

 Avater on a large scale, to supply a trout hatchery in that way. 



