390 Mr. V. N. Nene. On a Method of Tracing 



simple harmonic waves of an approximately known period was in its 

 infancy. The aim was to see whether on barometer observations there 

 was any influence of lnnar period, the duration of which is about 

 30 days. The trial which we are going to describe was made in the 

 earlier period of 1878, when the barograph tabulation was under con- 

 sideration. Daily means of barograph tabulations, corrected to 

 standard barometer No. 58, for this same period, may be found in the 

 " Bombay Magnetical and Meteorological Observations, 1871 to 1878," 

 pp. 60 and 61. The difference between the daily means, corrected and 

 uncorrected to standard instrument, is very small, and not varying 

 from day to day more than (say) about two or three thousandths of 

 an inch, The treatment which was given to these daily means and 

 the results which followed from it may be considered satisfactory. 



47. In order to get the series in smooth-flowing numbers, we have 

 taken 15 as our working value of m, and found first mean series. Then 

 this series has been taken for further operation, and by taking 45 as 

 our working value of m, we have found first, second, &c, up to fifth 

 series of remainders. The first, third, and fifth series of remainders are 

 curved in fig. 5 in plain, dotted, and interrupted lines respectively, 

 with the same scale and on the same zero line. Looking at the plain 

 curve, we see that there are nine turning-points of minima, the dura- 

 tion thereof being moderately uniform. If we take the first minimum 

 in the middle of the small gap that occurs in the curve, we have in 

 298 days eight periods. Thus an average duration of one period is 

 about 37 days. Again, if we count the days from the second mini- 

 mum, we have 258 days in seven waves, and thus an average duration 

 is still about 37 days. Thus, instead of the lunar period of 30 days, 

 we find a 37-day period. From this it is clear that if there be lunar 

 period in the series at all, the amplitude of it must be much smaller 

 than the 37-day period. 



48. The object of drawing the three curves on the same zero line 

 and with the same scale is to show graphically the process of swelling 

 the waves as the operations increase and of their appearance, as in the 

 case of the third wave, which disappears in the first series of 

 remainders. The object is also to impress the necessity of making 

 smooth-flowing numbers before taking them for operation ; as in the 

 case of second, third, fifth, and seventh waves, all the irregular move- 

 ments in the first series of remainders are found to appear in the third 

 and fifth series of remainders. With these remarks we conclude with- 

 out giving the numbers from which the present curves are formed. 



Second Application. 



49. In order to test the reality of the period of about 37 days on a 

 large scale, we have taken a series of weekly means of barometer 

 observations at Bombay, commencing from 1st January, 1848, and 



