292 Dr Gairdner's Observations during a Voyage^from 



• From which : 



North Pacific Torrid Zone, Mean, 30.093 

 South Pacific Torrid Zone, 29.965 



Mean of North and South Pacific, 30.029 



North Atlantic Torrid Zone, Mean, 30.003 

 South Atlantic Torrid Zone, 29.895 



Mean of North and South Atlantic, 29.949 



I was chiefly led to the calculation of these barometric 

 means, by the idea, that perhaps a difference of level between 

 the two oceans might be the result. May not the irregularities 

 resulting from the motion of the ship, winds and weather, be 

 lost in the number of partial observations, giving errors both in 

 excess and defect ? If they are of any value in this point of 

 view, they would indicate the level of the Pacific to be lower 

 than that of the Atlantic Ocean. To find the amount, using 

 Dabuisson's Portative Table, given in his Geognosie, i. 467. :^ 



30.029 In. = 768.7 mills. _= elevation, 76 

 29.949 1=: 760.7 = . 97 



Difference, 21 metres = 69 feet, 



neglecting all corrections for temperature, &c. as these will 

 operate in the same direction, and nearly about the same 

 amount, on both barometric columns. N. B. The cistern of 

 the barometer used was about 10 feet above the level of the wa- 

 ter. 



My observations on the temperature of the surface strata of 

 the ocean were daily made throughout the voyage at 7-8 a. m., 

 noon to 2 p. M., and sunset. It would occupy too much space 

 to give here the detail of these observations. I shall therefore 

 merely give you their abstract, following two methods, by com- 

 paring which, more correct conclusions will be formed than by 

 either method singly. 



Method 1. — Where the temperatures given are the means of 

 the observations on the days when the parallels indicated were 

 crossed. 



