294 



A former connection with the ocean is claimed for a number 

 of the Swiss and Italian lakes by Dr Forel and Professor Pavesi, 

 and the Norwegian lakes by Loven and Sars, on the ground 

 of the occurrence of marine forms of the crustaceans and other 

 classes. For a summarized account of these researches see 

 Pavesi. Arch, de der.eve, 1880, in. I. 



Temperature of Lakes. The earliest reliable temperature 

 observations in lakes or seas are those of Saussure, and they 

 are to be found in his charming Voyage dans les Alpes. He 

 was the first to obtain thoroughly trustworthy observations in 

 the deeper waters of the lakes. He used for this purpose an 

 ordinary thermometer whose bulb was covered over with several 

 thicknesses of cloth and wax, so as to render it very slowly 

 conducting. He was in the habit of leaving it down fourteen 

 hours, and then bringing it up as quickly as possible and 

 immediately reading the temperature. He did not, however, 

 trust to his thermometer not changing its reading while being 

 brought up, but by an elaborate series of experiments he 

 obtained corrections, to be applied when the thermometer had 

 to be drawn through more or less water of higher temperature. 

 His observations are collected in the following table along with 

 those of Jardine in some of the Scottish lakes, at the beginning 

 of the century: 



