APPENDIX. 



(See note on preceding page 2.) 



Extract from Appendix No. XL 2d volume of the Narrative, p. 405, on the Determination of 



Temperatures. 



* * * * Sir Edward Parry, and more recent Arctic voyagers, have sbowii that 



there is a differeuce, amounting sometimes to two degrees, between the temperatures adjacent to, and at 

 a distance from, the vessel. This was abundantly confirmed by our experience. During the intense cold 

 of our winters, the instruments became very impressible to artificial elevation of temperature. The 

 approach of the observer, the use of the lantern, the neighborhood of articles taken from a heated apart- 

 ment, &c. &c., were at once perceptible in our records. 



Except in naval expeditions, Arctic temperatures, whether Asiatic or American, have been recorded 

 with a limited number of instruments. The results of these must be received with extreme caution ; for 

 the differences which alcoholic thermometers exhibit, at temperatures below the freezing point of mercury, 

 are so varying as to require a large number of comparisons, and upon many instruments, to determine 

 their proper correction. It was not uncommon for thermometers which had given us correct and agree- 

 ing temperatures as low as —40°, to show at —60° differences of from fifteen to twenty degrees. Such, 

 too, was the case with the well-constructed instruments of Sir James Ross at Leopold Harbor. 



To give an example of this, I may refer to the record of six thermometers suspended near each other, 

 as above described, and observed for purposes of comparison at noon February 5th, 1854. 



_71o, _G3°, —54°, —53°, —50°, and —50°. 

 All of these, at temperatures above -40°, agreed within 1°.8, and were selected as the most consistent 

 of nearly thirty spirit thermometers. 



At 9 A M of the same day, eleven similar thermometers gave, under like circumstances, a mean of 

 68°, the extreme readings being -56°.4 and -80°. For the purpose of obtaining the most probable 

 temperature from these conflicting records, my first impulse was to reject the lowest (coldest) extremes, 

 and take the mean of those which accorded best; but upon advising with our astronomer, Mr. Sonntag, 

 I determined to take the mean of all without rejecting any, the view which he took being simply that 

 those instruments which indicated the extremes in the low scale had never, in temperatures above —40 , 

 shown any anomaly which deprived them of an equal claim to confidence with the rest, and that there 

 was no reason, & priori, to consider the results which they gave as less probable than those shown by 



the others. , „ ,, > 



t In a word, I adopted the views of Professor Airy, as published in the 95th number of the Aviertcan 

 Astronomical Journal. The causes which had produced the errors were mostly unknown, and the 

 quantity to which these errors might amount was entirely so. . , ■, x, ^ ^.i. 



Our thermometers were made with great care by Tagliabue, of New York. But, independently o o her 

 mechanical sourees of error, I am obliged to say that I do not regard the contraction of colored alcohol, 

 at very low temperatures, as sufficiently investigated to enable us to arrive at the causes or the quantity 

 of error. In most of the spirit thermometers, the uniform thickness of the tube was tested before leav- 

 ing New York; and the freezing of carefully distilled mereury, which I had taken with me for the pur- 

 pose gave excellent determinations of absolute temperature. 



But it may not be uninteresting to state that the freezing point of this metal varied between -38 .5 

 and -41°.5, and that its rate of contraction as a solid was so uniform that, m our long and excel- 



