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in which it is comparatively slow ; the quick hours being those of 

 the day, the slow hours those of the night. 



Thus far the notice we have taken of the Pekin results has been 

 limited to the diurnal variation which we find when we take an 

 average of the whole year, and which we may theoretically suppose 

 would take place in every month of the year if the sun were always 

 in the plane of the equator. But similar investigations had already 

 made known to us the existence of a semiannual inequality, having 

 opposite phases according as the sun has north or south declina- 

 tion; with turning epochs about the times of the solstices, and 

 the phases passing into each other about the times of the equinoxes. 

 I have already, on a former occasion (Proceedings of the Royal So- 

 ciety, May 18, 1854), submitted to the consideration of the Society 

 the concurrent evidence from three stations, Toronto, Hobarton, and 

 St. Helena, of the existence of this inequality, and of the almost 

 uniform character of its phases at those stations, from which I ven- 

 tured to infer the probability that an inequality having a similar cha- 

 racter would be found to be a general phenomenon. I am now 

 able to add to the evidence which was then adduced, a representation 

 of the semiannual inequality at three additional stations, viz. at the 

 Cape of Good Hope, of which the particulars in detail will be found 

 in the 2nd volume of the ' St. Helena Observations,' at the Kew Ob- 

 servatory, taken from the hourly tabulations from the photographic 

 curves obtained by the self-recording declinometer at that station, 

 and at Pekin, as shown in the following tabular view : 



Semiannual Means of the Solar-diurnal Variation at Pekin. 



As the correspondence of such phenomena is often far better 

 judged of by the eye, when exhibited in the form of curves, than by 



