NO. 17.] THERMOMETERS. 11 



They were compared in April, 1893, with tiie standard thermometer of 

 the Norwegian Meteorological Institute, whose corrections to the hydrogen 

 thermometer are known. 



The results of these comparisons were as follows: 



SoDERBERG 



No. 0° 



105 + 0-20° 



106 + 0-20 



107 + 0-20 

 109 + 0-20 



111 +0-20 



112 +0-20 

 114 + 0-20 

 118 + 0-20 



It was intimated that the zero-points would probably rise with time; and 

 it will be seen by comparison with the adopted corrections, that this has 

 also been the case. Unhappily not one of these thermometers has been brought 

 back in a sufficiently unchanged state to allow of these corrections being 

 verified. The determination of the zero-points on the voyage was attended 

 with difficulty, owing to the fact that snow or ice that did not contain salt 

 was almost unobtainable. The most trustworthy observations were made 

 with hoar-frost collected on board. 



II. 4 toluol thermometers made by Tonnelot in Paris, the stem divided 

 into whole degrees C, cylindrical bulbs. They were compared at the Bureau 

 International des Poids et Mesures (Sevres) at low temperatures in May, 1892, 

 and their zero-points were determined at the Meteorological Institute in Chris- 

 tiania in April, 1893. 



The corrections to the hydrogen thermometer were as follows: 



Tonnelot Correction at 



No. 0° —23° —30° —52° —53° -54° —65° 



4992 +0-20° -0-02° -0-24° 



4993 +0-20 +0-07 +0-03° 



11001 +020 +0-08° +0-01° +0-07° 



11002 +0-20 -0-16 -009 —0-15 



