308 Mr. Daniell's Reply 



will doubtless give him credit for the patience and perseverance 

 ■with which he must have sought for opportunities, inconsistent 

 to be sure with the object which he had in view, but at the same 

 time remarkable and rare. 



We have seen with what ill fortune a gentleman of Captain 

 Sabine's acquirements attempted to place his thermometers so as to 

 obtain something like an approximation to the power of the sun ; 

 and that, during the course of a complete year, with selected 

 opportunities, he did not once succeed (for once will be sufficient to 

 establish the argument) in obtaining the object which he had in view. 

 Let us now turn to the unpremeditated observations of those who, 

 having no object in view, and being unprepared with even the 

 rough apparatus which has been described, had their attention 

 called to the prodigious power of the sun's rays in high northern 

 latitudes. Chance now brings about what science could not effect, 

 and the thermometers are all at once placed in the most favourable 

 positions for indicating the extreme effects ! The bulb of the in- 

 struments in this instance were not covered with black wool, or 

 even blackened superficially, but then " Qui ne salt combien la 

 force rdfl^chissant de la neige est considerable ? II aurait fallu 

 faire, par le calcul ou par I'experience, la part de cette reflexion, 

 avant de comparer les observations de Londres avec celles du 

 Capitaine Parry." Let M. Gay-Lussac fairly make the calculation 

 of the effects of this reflection on one side, and of the blackened 

 bulb on the other, and I do not fear that my reasoning will be 

 shaken by the result. 



To assist in forming a right conclusion upon the subject, let the 

 following additional fact, extracted from Captain Lyon's interest- 

 ing Journal, be taken into consideration ; the place of observation 

 and the date are, Igloolik, 16th February: — "I observed, even 

 while the temperature in the shade was 35° below zero, that fine 

 powder of snow melted under the influence of the sun when 

 sprinkled on a stick covered with soot ; thus making a difference 

 of temperature existing at the same time as great as 67° and up- 

 wards." — Lyons Journal, p. 389. 



Here the coating of soot renders the experiment very closely 



