480 Royal Society :— 



In the different stations in the northern hemisphere, where the ex- 

 treme deflections have been found to take place at the same hours of 

 solar time, the differences in the direction of the magnetic meridian 

 have not been less than 70°, equivalent to a difference of solar time 

 of between four and five hours. 



I ought not to close this paper without adverting to the success 

 which has attended Mr. ScatchkofFs employment of native Chinese 

 as his assistants in the work of the Pekin Observatory, holding out 

 as it does an encouraging example to Directors of Observatories who 

 may be similarly circumstanced. A very close test of the care and 

 fidelity with which observations have been made and recorded is fur- 

 nished by the lunar-diurnal variation, deducible from them when they 

 have been re-arranged under the lunar hours to which they severally 

 belong. Thus tested, the Pekin observations show no inferiority to 

 those of other stations which have been similarly examined. 



It is understood that the observations, which were discontinued at 

 Pekin at the end of 1855, are about to be recommenced, or have been 

 so already. It is greatly to be desired that hourly obervations of 

 the Horizontal and Vertical Forces should be combined with those 

 of the Declination at this important station. The self-recording ap- 

 paratus of the three elements which has been in action at Kew during 

 the last two years, has been found, by the reduction of its tabulated 

 values at hourly intervals, to be in no respect practically inferior to 

 the method of eye-observation, whilst it possesses many advantages 

 which are peculiarly its own. The tabulation from the Photographic 

 Curves, as well as the reductions, might be made, if more convenient, 

 at the central Physical Observatory at St. Petersburgh. 



March 15. — Sir Benjamin C. Brodie, Bart., President, in the Chair. 



The following communication was read : — 



" Analysis of my Sight, with a view to ascertain the focal power 

 of my eyes for horizontal and for vertical rays, and to determine 

 whether they possess a power of adjustment for different distances." 

 By T. Wharton Jones, Esq., F.R.S. &c. 



Besides the well-known differences of sight in respect to farness 

 and nearness, there are differences in respect to the power of the 

 eyes of different persons to bring the rays of light to one exact focus. 



From observations and experiments in which I have for some time 

 been engaged, I have been led to suspect that astigmatism or inca- 

 pacity of the eye to collect all the rays of light which enter it to 

 one exact focus, is, if not the rule of sight, at least of very common 

 occurrence. I do not here refer to the cases in which astigmatism is 

 of so exaggerated a character as to be a positive defect of sight. 



It would be of great importance, both in a scientific and practical 

 point of view, to possess some accurate data as to the frequency of 

 the occurrence of astigmatism ; but such can be obtained only by a 

 number of different persons — qualified observers — contributing each 

 an analysis of his own sight. I have thought, therefore, that by 

 bringing under the notice of the Royal Society an analysis of my own 

 sight, some of the Fellows and others accustomed to exact observations 



