268 



E. F. PIGOT. 



a very euphonious term, I admit, especially if the second 

 "g" is pronounced soft, but sufficiently expressive — ) is the 

 substitution of photography for the traditional visual obser- 

 vations, thus to a large extent eliminating the element of 

 *■' personal equation." By this means actual records (geo- 

 gyrograms) of the Earth's rotation can be measured at 

 leisure by a number of persons, each a check on the others, 

 and quantitative determinations obtained, I believe, of a 

 degree of accuracy at least equal to that obtainable by the 

 visual methods hitherto employed. 



These somewhat hurriedly-prepared notes do not allow 

 at present of describing various other details of the method 

 of procedure adopted to ensure precision, e.g., the method 

 of releasing the bob, removal of residual torsional oscillation 

 in the bob, protection from air currents, etc. 



I also postpone for the present giving any quantitative 

 results of these experiments, (as well as of a second series 

 also in progress, in the dome of the Queen Victoria Markets, 

 Sydney, with a pendulum no less than 26 metres long) until 

 the above mentioned improvements have been carried out, 

 both series having been somewhat of a tentative character. 

 In a subsequent paper, I hope to give the full results of all 



the experiments. 



■ 



In conclusion, I wish to express my sincere thanks to 

 Prof.Pollock,D.Sc. f f.r.s., Prof. Von wilier, B.Sc, Prof. Cotton, 

 m.a., f.g.s., Messrs. Ranclaud, B.Sc, J. Lane Mullins, J.P., 

 Murday and Breden, for valuable suggestions and kindly 

 help; to the Surveyor-General and Mr. R. H. Oambage, 

 f.l.s., for the loan of instruments for the new visual method 

 I have adopted at the Queen Victoria Markets; and to the 

 Lord Mayor, for having been so good as to grant me the 

 use of this fine building for the research. 



