Report of Magnetical Observations at Falmonth Observatory. 557 



Report of Magnetical Observations at Falmouth Observatory 

 for the Year 1893. Latitude 50 9' 0" N. and Longitude 

 5 4' 35" W. ; height, 167 feet above mean sea-level.* 



These observations have been made by instruments purchased from 

 the Government Grant Fund administered by the Royal Society. 



The Observatory having been comparatively recently established, 

 the Vertical Force self-recording instrument is not yet in thorough 

 working order. It is hoped in future to publish complete records of 

 all three elements. 



Photographic curves of Magnetic Declination and of Horizontal 

 Force variations have been taken regularly throughout the past year, 

 and the magnets have worked satisfactorily. 



The scale values of the instruments were determined in April last. 

 The following values of the ordinates of the photographic curves 

 were then found : 



Declination, 1 cm. = ll'-7. 



Bifilar, April 7th, for 1 cm. 8 H., = 0'00055 C.G.S. unit. 



This latter value not being in accordance with the prescribed 

 standard scale, the sensibility of the magnet was increased, and a 

 second series of deflections made on April 10th, when the value was 

 determined for 1 cm. H. = Q'00050 C.G.S. unit. 



No violent magnetic disturbances have been recorded during the 

 year ; the principal movements occurred on the following dates : 

 February 5, March 26, July 16, August 6, 7, 18, and November 1, 2. 



Observations with the Absolute Instruments have been made 

 monthly, of which the following is a summary : 



Determinations of Horizontal Intensity, 34. 



,, Inclination, 35 sets of four. 



absolute Declination, 33. 



The results in the following tables, Nos. 1, 2, 3, 4, are deduced 

 from the magnetograph curves which have been standardised by 

 observations of deflection and vibration. These were made with 

 the Collimator Magnet marked 66A, and the Declinometer Magnet 

 marked 66c in the Unifilar Magnetometer by Elliott Brothers, of 

 London. Table No. 5 is deduced from these observations. 



* The records of the Falmonth Magnetic Observatory hare hitherto been 

 published in the 'Journal of the Royal Cornwall Polytechnic Society.' The 

 committee of management having obtained leave to communicate their annual 

 magnetic report to the Eoyal Society, it will henceforward be printed in the 

 ' Proceedings.' The results are worked up in the same way as those obtained at Kew, 

 and the reports of the two observatories will in future appear simultaneously. E. 



VOL. LVI. 2 P 



