94 Chemical and Physical Notes 



or two minutes after the thermometer. This refers only to 

 oceanic work. The physicist must himself test the actual 

 thermometers which he has on board by observing them in 

 still water and when moved at certain velocities in water, and 

 from his own observations he will form his own opinion of 

 how long the particular instruments with which he is supplied 

 have to be left down, and then he will use his knowledge to 

 guide his practice. 



Application of Calorimetry to Hydraulics. An interesting 

 example of the application of calorimetry to problems of 

 physical geography is afforded by some hydraulic experi- 

 ments made by the writer in the Engadine in the summer 

 of 1894. About a mile below the end of the Morteratsch 

 glacier, the muddy stream which proceeds from the glacier 

 is joined by the perfectly clear waters of the stream which 

 descends from the summit of the Bernina pass, the waters 

 of which drive the machinery for the supply of electricity to 

 Pontresina. In the afternoon the glacier stream is running 

 strongly, and its temperature was found to be i C. The 

 temperature of the water of the Bernina stream was nC. 

 Two or three hundred yards below the confluence, where the 

 waters had been well mixed, the temperature of the water 

 was 2'5 C. If we represent by M the flow of the Morteratsch 

 and by B that of the Bernina stream, we have the relation 

 M \ B :: 10 : 1*5, whence we have B = O'i$M, or the stream 

 below contains 85 per cent, of Morteratsch water and 15 per 

 cent, of Bernina water. 



Temperature of Insolation. In a meteorological outfit it is 

 usual to include a thermometer with blackened bulb enclosed 

 in an external glass tube. This is to be exposed to the direct 

 rays of the sun until it rises to a temperature which remains 

 stationary. This temperature is to be observed. When taken 

 in connection with the temperature in the shade this is to 

 furnish information regarding the calorific action of the sun's 

 rays. It is in a position to furnish reliable information of 

 this kind only if the thermal mass or water value of the bulb 

 and its term of cooling are known. These are not commonly 

 supplied. Even if they were supplied it is doubtful if the 



