93 
length of the pendulum vibrating seconds . 
distance between the knife edges, we may remark that when 
the slider was at 29 divisions, the number of vibrations (the 
great weight being below) was, 86057,85 and in defect; and 
when the slider was removed to 19 divisions, the number of 
vibrations was 86059,4,1 and in excess. The true number of 
vibrations then is evidently between the two, and the utmost 
extent of error in using either of these numbers must fall 
short of 1,73 their difference when reduced to the same tem- 
perature. But if the mean be employed in the computation, 
the length of the pendulum will be found to differ only about 
four ten-thousandths of an inch from the mean result given 
in the foregoing table. 
It may not be unnecessary to add that every experi- 
ment made has been retained ; nor do I consider any one as 
less entitled to credit than the rest, excepting that marked A, 
in the table ; and that, only because the rate of the clock was 
not observed on the day of the experiment, but was taken to 
be the same as the rate of the following day. 
The length then of the pendulum vibrating seconds in 
vacuo at the level of the sea, measured at the temperature of 
62° of Fahrenheit, appears to be 
Inches. 
By Sir G. Shuckburgh’s standard - 39,13860 
By General Roy’s scale - - 39 T 3717 
By Bird’s Parliamentary standard - 39,13842 
the latitude of the place of observation being 
51 0 31' 8", 4 north.* 
• The latitude was deduced from the data contained in the trigonometrical sur- 
vey; Mr. Browne’s house bearing from Portland Chapel 74 0 . 38'. 5c". west from 
the north, the distance being 283 feet. This differs only o",i from the latitude 
determined by Mr. Browne from a great number of observations. 
