220 



BULLETIN OF THE BUREAU OP FISHERIES. 



variable in these lakes, and to it are due most of the striking differences in the work 

 required to warm the deeper strata. In the 30 to 40 m. stratum of Canandaigua Lake, 

 for instance, it required about 70 g. cm. to put 1,230 cal. into place. In the corre- 

 sponding stratum of Cayuga Lake it required 93 g. cm. to place 1,400 cal. The 

 difference in calories is about 14 per cent, in work over 30 per cent. This is mainly 

 due to the difference in loss of density. At 6.1°, the temperature of Canandaigua Lake, 

 this is 35 points,' and at 6.4°, the temperature of Cayuga Lake, it is 46 points, or over 

 30 per cent greater. 



Table 4 shows that a great amount of work is necessary to produce by mixture 

 the high temperature of the upper strata; it shows also that an almost incredibly small 

 amount of work is needed to carry considerable heat to great depths if only it involves 

 but little rise of temperature. Note, for example, Seneca Lake, where 42 cal./cm.^ 

 of surface are transported to a mean depth of 55 m. for an expenditure of about i g. cm. 

 On the other hand, in the corresponding stratum of Canandaigua Lake, each gram 

 centimeter of work transports only about 18 cal. The difference is due to the much 

 greater rise of temperature in the smaller lake — reaching 5.2° instead of 4.5° in Seneca 

 Lake. 



Table 5. — Detail for Seneca Lake of the Facts op Distribution of Mean Summer Heat Income. 



[Note. — T.=temp€rature in degrees centigrade; i-D=loss of density due to warming: RTXZ=factor. reduced thickness 

 midtiplied by depth. Direct=work done in behalf of stratum in question: Dist. = work done in stratum in question: Cal.= 

 calories of summer heat income in stratum. All expressed in units per square centimeter of lake surface. See fig. 3. p. 

 339; also Birge, 1916, p. 349,355-1 



Depth in meters. 



2-3 



3-4 



4-5 



S-6 



6-7 



7-8 



8-9 



9-10 



xo-il 



11-12 



12-13 



13-14 



14-iS 



15-16 



16-17 



IT-18 



18-19 



19-20 



20-95 



25-30 



30-40 



40-5° 



50-60 



60-70 



70-80 



Below So . 



Total. 



20.4 

 20. 2 

 20. 3 

 20. 1 

 30. o 



30. O 

 19.9 

 19.8 



19- 7 

 19. 7 

 19. 6 

 >9-5 

 19.3 

 18.8 

 18.6 

 17.4 

 l6. o 

 M-S 

 13-6 

 13. O 



10. 6 



8.0 

 6.3 



5-4 

 4-6 

 4-S 

 4-3 



I-D. 



o. 001853 

 1815 

 181S 

 1790 

 1770 

 1770 

 1749 

 1729 

 1708 

 1708 

 1688 

 1668 

 1628 

 IS19 

 1491 

 1269 

 1030 

 0844 

 0674 

 047s 

 0338 

 0134 

 0042 

 0016 

 0003 

 0003 

 0001 



RTXZ. 



49.5 

 147 

 240 



333 



423 



513 



592 



675 



748 



827 



914 



989 



1.076 



1,147 



1.333 



1.304 



I.370 



I. 453 



1.517 



1.580 



9.050 



10.735 



26. 040 



31.130 



35. '20 



38. 005 



45.280 



Direct work. 



G. cm. G. em. 



9.2 



26.8 



43-7 

 59-6 

 74-9 

 90. 6 

 103.6 

 117- 8 

 127.9 

 141-4 

 154- S 

 165. 2 

 176 o 

 176. o 



183-3 



165. 7 

 141. I 

 123-4 

 102. 4 

 74-6 



581-3 



855-0 



607- 3 



396.8 



132-7 



109- 2 



49-8 



lo 5 



7-6 



4-5 



Dist. work. 



G. cm. 



284.6 

 366. 5 

 348.8 

 231- S 

 213- 6 

 197.0 

 180.8 

 164-9 

 149-6 

 134.6 

 119.8 

 105. 2 

 90-9 

 76 s 

 65.6 

 S3-0 

 43-3 

 35-6 

 29-3 

 34. 6 



G. cm. 



826-9 



185.8 



80.8 



35- 7 



29- 5 



9- I 



2-9 



1-3 



.4 



2, 874- 4 



1,624 



1,588 



i>555 



1.53° 



1.504 



1.488 



1.447 



1.422 



1,382 



1,366 



1.357 



1.333 



1,316 



1,258 



1.241 



I. 136 



996 



S96 



787 



648 



2.653 



1.560 



I. 714 



969 



485 



263 



i6s 



347 



34,030 



Depth 



G. cm. 



2.874-4 



2. 589- 8 



2. 323. 3 



3.074. s 



1.843.0 



1.639.4 



1.432.4 



I, 251. 6 



1,086. 7 



937- I 



802.5 



682.7 



577-5 



4S6. 6 



410- I 



345- 5 



292-5 



249- 2 



213-6 



184.3 



159 7 



78.9 



43-2 



13-7 



4. 6 



1-7 



-4 



Cal. 



34. 030 

 32.396 

 30,808 

 29.253 

 27. 723 

 36.219 

 24.731 

 23.284 

 21.862 

 30,480 

 19. 114 

 17.757 

 16,434 

 iS.ioS 

 13.850 

 13,6*9 



1 1 . 483 

 10,487 

 9,591 

 8,804 

 8,156 

 SIS03 



3.943 



2,229 



1,360 



775 



512 



347 



* By a "point" is meant a decrease in density of one part per million. The density of water at 6.1 as compared with that 

 at 4.0* is 0.999965. The loss in density is. therefore. 0.000035 and this represents the loss in weight of the lighter surface water at 

 5.1*. and, therefore, is one factor in determining the work to be done in pushing it down into deeper and cooler strata. For con- 

 venience in computation this factor is taken as a positive quantity and a whole number is stated as 35 points. (See Birge, 191^ 

 p. 391-) 



