OF THE OBSERVATIONS FOR ATMOSPHERIC PRESSURE. 105 



the correction for index, +0.007, and (he reduction to the level of the sen, -f 0.005. 

 To the table 1 have added for comparison the values for Van Rensselaer Harbor 

 (also referred to the level of the sea by applying -f- 0.005). 



Monthly Mean Readings of tfte Barometer at the level of the Ska, and at 32° Fahr. 



1857-8. 

 Month. Baffin Bay. 



Lat. 7 2 .5 



January . . . 29.532 



February . . . 29.640 



March . . . 29.893 



April . . . 29.940 



May . . . *30.014 



June . . . 29.817 



July . . . 29.753 



August . . . 29.736 



September . . 29.735 



October . . . 29.756 



November. . . 29.665 



December . . . 29.570 



Mean . . 29.755 29.938 29.775 



It should be remembered that the monthly means in the first column were 

 obtained while the ship was drifting and sailing in Baffin Bay, on which account 

 the annual fluctuation may not appear as plainly as if the ship had been stationary 

 in the middle latitude 72°.5 N. 



The maximum in each series has been marked with an asterisk (*) ; it occurs 

 either in April or May. The occurrence of the minimum does not agree at these 

 stations; in Baffin Bay it occurred in January, at Port Kennedy in July, and at 

 Van Rensselaer Harbor in September — showing plainly that more observations are 

 required to fix the season or month in which it takes place on the average. 



The preceding monthly values are represented by the formulas : 



1. For Baffin Bay, 1857-8— 



B= 29.755 + 0.155 sin (0 + 304°) + 0.113 sin (26 + 236°) 

 (Greatest difference between an observed and computed value = 0.04 inches). 



2. For Port Kennedy, 1858-59— 



B = 29.938 + 0.137 sin (6 + 17°) + 0.10G sin (20 + 232°) 



(Greatest difference between observed and computed values; in October 13 



in November, +0.11). 



3. For Van Rensselaer, 1853, '54, '55— 



j5= 29.775 + 0.079 sin (6 + 4°) + 0.044 sin (26 + 194°) 

 Expressed in inches, and 6 counting from January 1st, and at a rate of 30° a month. 

 The computed annual range, or the difference between the highest and lowest 

 monthly mean, is as follows : — 



Baffin Pay 0.44 inches. 



Port Kennedy .... 0.41 " 

 Van Rensselaer . . 0.21 " 



