REPORT OF THE SECRETARY. 35 



while the southwest always increases the temperature, especially in 

 the winter season. The most intense cold was experienced when the 

 air was perfectly calm, and this appears to be the general rule in the 

 arctic regions. The effect of the various winds on the whole is small, 

 not exceeding an elevation or depression of more than a degree and 

 a half from the mean. 



The effect of the snow and rain on the temperature is far greater 

 than that of the wind. On an average in winter, during every fall of 

 snow, the temperature was elevated 8°. 6, and in summer fell a degree 

 and a half during a fall of snow or rain. The number of days in which 

 snows fell was 94, those in which it rained were 15, during the whole 

 period of eleven months. 



The effect of clear and cloudy weather on the temperature is next 

 considered, and from the result of 82 clear days in winter, it is found 

 on an average 3| degrees below the normal temperature of these 

 days. In summer, from the observations of 41 clear days, the tem- 

 perature was higher eight-tenths of a degree. In winter, during 31 

 cloudy days, the temperature was seven degrees above the normal; and 

 in summer, during 48 cloudy days, the temperature was 2°. 1 lower 

 than the normal. 



From the foregoing it appears that a clear atmosphere produces op- 

 posite effects in summer and in winter, and this is, without doubt, due 

 to the greater amount of vapor in the former than in the latter season. 

 During a clear day in winter the air is almost entirely deprived of 

 vapor, and radiation goes on with full energy, uncompensated by 

 rays from the sun, except those which are very oblique; while in sum- 

 mer the more intense rays of the sun penetrate the vapor, while the 

 less intense heat from the earth cannot escape through the aqueous 

 stratum. 



The last discussion relates to the direct heating power of the sun 

 and the record of temperatures observed during the excursion to the 

 extreme northern point reached. The temperature in the month of 

 May, 1861, was ten degrees lower along the coast of Kennedy chan- 

 nel, indicating a colder climate as the explorer went north, but whether 

 this would be the case during the other parts of the year remains 

 yet to be verified. 



The observations on atmospheric pressure are not as complete as 

 those on the temperature, the observations between 10 p. m. and 6 

 a. m. being frequently wanting. All the readings were reduced to 

 the temperature of 32° Fahrenheit. 



The diurnal fluctuation as given by these observations, as well as 



