by Optics, the Translatory Motion of the Sola?' System. 499 



are based were all (with a few exceptions) made at or near mid- 

 day. On this account I thought that the corrections due to the 

 motion of the instrument might be neglected in calculating the 

 results, since in the final mean such corrections must, for the most 

 part, disappear. 



In proof of the accuracy of the theory here established, I will 

 give a few of the observations made last year at the commence- 

 ment of October. They have reference to the double line D in 

 the fourth interference spectrum. The light was always inci- 

 dent from south to north. The second telescope and the grating 

 were readjusted every day. 



Table III. 



Time of observation, 

 in 1862. 



29 4 =0. 



Remarks. 



h 

 fll-4 a.m. 

 Oct. 5 -j 3-58 p.m. 



[ 5 P.M. 



Oct. 91 o. 7 a„^ 



10 } 3 u P - M - 



f 9-5 A.M. 

 Oct. 11 \ 1 P.M. 



[ 3-75 p.m. 



62 55 38 

 62 55 53 

 62 56 7 



62 56 



62 55 51 

 62 55 58 

 62 56 7 



> Mean of three observations. 

 Mean of six observations. 

 Mean of six observations. 



1 Mean of two observations. 



From the mean value of the wave-lengths corresponding to the 

 line D given in Table I. we deduce 



2e 4 =62 o 55'41"-2 = <£ ; 



and since this value must be very nearly free from any error due 

 to the motion of the instrument, it ought to agree with that fur- 

 nished by the observations in Table III ., after applying to the 

 latter the corrections due to the motion of the instrument. 



If X be the velocity of the solar system in a direction deter- 

 mined by the coordinates of the equator, 



D=34°5 and A=259°-8, 



the magnitude of the motion of the instrument from north to 

 south, due to the motion of the solar system, will be 



X cos b = X [cos D sin P cos (A — *) — sin D cos P] , 



where P denotes the altitude of the pole, and >fc the sidereal time 

 of the observation. 



Por Upsala, therefore, we shall have the formula 



X[0'713 cos (259°-8- #) -0*284], 



The velocity of the instrument, in the above direction, due to 



