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SOME EESULTS DEEIVED EROM THE CONSTANT 

 Vx\LUES IN THE PEEIODIC FORMULA. 



By J. E. Sutton, M.A. (Cantab.). 



(Read May 28, 1902.) 



In a previous communication dealing at some length with certain 

 pressure and temperature observations made in South Africa,"^' I 

 omitted — chiefly for want of time — to discuss the coefficients and 

 angles derivable from Bessel's periodic formula. The omission is 

 to be regretted, because, apart from the no little interest of the 

 results, a number of errors both of calculation and of faulty copying 

 would have been detected in such values as were given. But having 

 had reason lately to compute the periodic constants for a number of 

 places, as opportunity offered, I have made a synopsis of them here, 

 correcting also the errors which were found in the MS. of the 

 previous paper which, as it fortunately happened, had not been 

 destroyed. 



The formula is, for monthly co-ordinates — 



(X = ^9 + <^i sin (x\i + m . 30) 



+ «2 sin (A3 + 2 . m . 30) 



+ . . . 



+ cin sin (A„ + n . m . 30) + . . . 



where a is the value required, 



2) is the mean of the year, 



A„ = tan-i^J,/^,,, 



(^n = i^«/sin A,, = 2«/cos A„, 



2)^ and q,^ being the known coefficients in Lambert's formula ; a,^ 

 and A,j the respective amplitude and phase-time of the harmonic 

 constituents. 



* " Some Pressure and Temperature Results, &c.," read in April last, but not 

 yet (April, 1902) printed. 



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