VOL. XLViri.] PHILOSOPHICAL TRANSACTIONS. 371 



after he rose. The doctor's leads were chosen, as being not far from Mr. Short's 

 clock, which was easily within call, in order to compare a second-watch with 

 the clock, at every observation. 



About half an hour after 4 in the morning of the 6th of May, Dr. Bevis and 

 Mr. Short went to Dr. Birch's house, where a series of observations was taken 

 with the above reflecting telescope moving parallel to the horizon, and the eye- 

 piece with the wires at right angles ; Dr. Bevis observing, and Mr. Short writ- 

 ing down the times. These were observations of the passage of the limbs of the 

 sun and mercury, by the vertical and horizontal wires of the telescope. 



About half an hour after 6, Dr. Bevis and Mr. Short went to Mr. Short's 

 house, the sun then shining into his windows, in order to be near the clock, 

 where observations were made in the same manner as before. Dr. Bevis observing, 

 and Mr. Short writing down the tftnes. 



The telescope, which hitherto had moved parallel to the horizon, was now 

 altered, to move parallel to the equator, and the eye-piece with the micrometer 

 was applied, about half an hour after ^ o'clock, Mr. Short observing, and Dr. 

 Bevis writing down the times of observation. 



Mr. Short observed the last internal contact of mercury with the sun, with \ 

 4-foot focal length reflector, magnifying about 135 times, at lO*" 5' 7'' by the 

 clock, uncertain to 1 or Z" ; and the total egress at 10*' 7' 42" by the clock; 

 uncertain to 5 or 6', the air then undulating through thin clouds. 



Dr. Bevis obscr\ed the last internal contact with a 2-foot focal length re- 

 flector, magnifying about 65 times, at 10*' 5', and the total egress at lO*" 7' 38", 

 by the clock. 



Mr. Sisson, at Beaufort Buildings in the Strand, observed the total egress at 

 10*' 7' 43", by Mr. Short's clock, through a 5-foot refracting telescope. 



Mr. Bird, at his house in York-buildings, observed the last internal contact 

 at 10'' 4' 57"; and the total egress at lO'' f 43", by Mr. Short's clock, through 

 a 9-inch focal length reflector. 



Mr. Smeaton in Furnival's-Inn-Court, Holbom, observed the total egress at 

 10*' 8' 30", by Mr. Short's clock, through a 6-foot refracting telescope. — He 

 suspects his time some seconds too late, a cloud having just passed off the sun, 

 when he perceived Mercury was gone. 



Mr. Canton, in Spital-square, observed the total egress at 10*' 8' 12", mean 

 time, through a reflecting telescope, 3-foot focal length. 



M. Short's house in Surry street, is 26' of time west of the Royal Observatory 

 at Greenwich. 



N. B. Mr. Short's clock, by which these observation* were made, was found 

 to be 28' slower than mean time. 

 ' 3 b2 



