384 PROCEEDINGS OF THE AMERICAN ACADEMY 



The following communication from Mr. E. W. Morley to 

 Professor A. Hopkins of Williams College, was presented. 



I have lately completed the reduction of my observations for the lati- 

 tude of Williams College Observatory, and thinking you might like to 

 have the result in some form which you can preserve, I transmit the 

 final equations of condition with their solution. You will find the mode 

 of observation fully described in Loomis's Practical Astronomy ; briefly 

 it is as follows. The telescope of the transit instrument being adjusted 

 so as to move nearly in the plane of the prime vertical, the star's time 

 of transiting the prime vertical is computed, together with its altitude at 

 that time, and the transit pointed in readiness. The star moves trans- 

 versely across the field, and is kept in the centre by moving the eye- 

 piece horizontally and the telescope vertically. Its transits over the 

 first ten wires are noted by the chronograph, the instrument is carefully 

 reversed and the transits over the same wires in a reverse order are 

 noted. After passing the meridian the transits over the same wires are 

 noted again, and the instrument reversed as before. This gives forty 

 passages to be noted, and, as a rule, ninety-six readings of the level. 

 As the interval between the east and west passages is from three to 

 five hours, there is but a small probability of getting a complete obser- 

 vation, and the loss of one of the four transits over each wire makes an 

 observation valueless. Unfortunately, during the time I was occupied 

 with the enclosed observations, the weather was so variable that a great 

 proportion of my observations were lost, seven eighths or more I should 

 think. The form of reduction is as follows. Take an observation of 

 a Lyrse, July 19, 1861. Transit over wire (1). 



East vertical, circle South . 



« " North 



West vertical, circle North 



« « South 



W. — E., circle South 

 W. — E., circle North . 



. 16 35 2.51 



20 28 26.00 



. 20 34 23.57 



4 5 20.26 



. 3 53 23.49 



1 59 40.94 



2 59.19 



9.9378777 



Cos i Difference 9.9999032 



^ Sum 



^ Difference 



Cos |- Sum 



h. m. 8. 



16 29 3.31 



4 



Cotang ^ (declination) .... 0.0969342 

 Cotang ;l (latitude) .... 0.0347751 



