104 Proceedings of Learned Societies. 
in each of five different gases (including air), and for each gas separately 
at the atmospheric pressure, and at the low pressure obtained by a good 
properties of the molecules which are present, through a range from 
great intensity down to a faintness which may elude our most powerful 
ea io 
at the extreme south of Spitzbergen, and rmine on @ 
favorable locality for the measurement of a ine. The result of the 
first years’ exploration has been the selection of stations, on hills ot 
proposed are o es. A convenient locality has also been 
for the base-line. _ The continuation of the preliminary survey to the 
Sear aoe ome is to be the work of the summer of 1864. The 
report of the geodesical surveyors has shown that the northern portion 
presents no impediments which may not be surmounted by courage and 
