306 



Intelligence and Miscellaneous Articles. 



the maximum density of water), Mr. Buchanan ascertained that, in 

 Loch Lomond, the temperature of the water gradually rose from 0° 

 at the surface to 2°'4 at 20 metres depth, but did not rise higher. 

 Must we infer from this the incorrectness of the classic theory of 

 the congelation of lakes? According to that theory, water, after 

 cooling throughout its mass down to 4° under the action of thermal 

 convection currents, becomes colder only at the surface, being stra- 

 tified in layers the colder the more superficial they are, conformably 

 to the order of their densities. The following observations prove 

 that the depths reached by Mr. Buchanan were not sufficient to 

 show the limit of the superficial cooling, which descends to a much 

 greater depth than has ever been supposed. 



I have repeated these researches in some Swiss lakes which are 

 deeper than those of Scotland. My soundings, executed with a 

 Negretti-and-Zambra thermometer, were made in the Lake of Morat 

 on December 23, 1879, and the Lake of Zurich on January 25, 

 1880. 



I. Lake of Morat. 



(Superficies 27*4 kilometres ; greatest depth 45 metres. The lake 

 began to freeze on the 18th December. Thickness of the ice on 

 the 23rd December, 11 centims. ; on the 1st of February, 36 cen- 

 tims.) 



Depth. 



December 23. 



February 1. 



Difference 



metres. 

 .. 



.... 0-36 



0'35 



-0-01 



5 .. 



.... 1*60 



1-90 



+ 0-30 



10 .. 



.... 2-00 



2-00 



o-oo 



15 .. 



.... 2-23 



2-45 



+ 0-22 



20 .. 



.... 2-46 



2-50 



+ 0-04 



25 .. 



.... 2-60 



2-50 



-0-10 



30 .. 



.... 2-66 



2-40 



—0-26 



35 .. 



.... 2-75 



2-55 



-0-20 



40 .. 



.... 2-70 



2-70 



0-00 



Means 



2-15 



2-15 



II. Lake of Zurich. 

 (Superficies 87'8 kilometres ; greatest depth 141 metres. The lake 

 froze during two days at the end of December, and then again 

 and definitively on the 21st of January. Thickness of the ice on 

 the 25th of January, 10 centims.) 



Depth. 



Temperature. 



Depth. 



Temperature 



metres. 





metres. 





. 



0-2 



70 . 



.... 3-7 



10 . 



2-6 



80 . 



.... 3-8 



20 . 



2-9 



90 . 



.... 3-8 



30 . 



3-2 



100 . 



.... 3-9 



40 . 



3-5 



110 . 



.... 3-9 



50 . 



3-6 



120 .. 



.... 4-0 



60 . 



-...., 3-7 



133 .. 



.... 4-0 



