1858.] Meteorological Observations on Parisnath Hill. 33 



Examining the barometrical curves 6 a — 13 a, separately, it 

 will be seen, that the barometrical curves of the single days, 6 a, 7 

 a, 8 a, 13 a, show, within very small limits, the same turning 

 points, the same general proportions, and preserve the same regula- 

 rity in their gradual transition from one hour to the next, as the 

 curves of the mean hourly pressures of the whole month. (9 a, 11 a) 

 and the whole year (10 a, 12 a). This uniform resemblance may 

 be shown for every day in the year. 



Turning now to those curves which represent the so-called pres- 

 sure of the dry air (6 b — 13 b), we observe, that the regularity of 

 the barometrical curves is at once broken, the moment we deduct the 

 tension of moisture. The irregularity produced by this operation 

 is, as might be expected from the nature of the hourly variations 

 in the tensions of moisture, greater in the curve of a single day 

 (6 b, 7 b, 8 b, 13 b,) than in that of a whole month (9 b, 11 b,) 

 and it is still partially apparent in the curves of a whole year 

 (10 b, 12 b.) The curves of dry pressure are not only dissimilar 

 to the barometrical curves, but differ also amongst themselves. A 

 correction of the possible error in the determination of the tensions 

 of moisture, particularly for single days, would not remove the 

 irregularity, as the error for all tensions is probably on the same 

 side and the magnitude of its variation comparatively insignificant. 

 The mean hourly tensions of moisture show locally a certain peri- 

 odic regularity, when the means of a larger number of days are taken. 

 But the magnitude as well as the course of their hourly changes varies 

 with the locality (9, 11) and with the seasons. Taking the curves of 

 single days, they will frequently be found to be entirely dissimilar 

 to the monthly and yearly means, and also unlike each other, and 

 often abrupt in their transitions Pigs. 6, 7, 8, 9, 10, 11, 12, 13. 

 This is not astonishing, if we remember how little is required to 

 effect sudden changes in the relative saturation of the watery 

 vapour in the atmosphere. I may add that the hourly variations 

 in* the curve of tensions of single days are often much greater than 

 the whole of the daily variation in the barometrical curve. 



Returning again to the barometrical curves, we find, that they 

 also slightly alter the magnitude of their daily variation with the 

 locality and with the seasons, but the uniform regularity in the 



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