158 Lovering on Magnetic Observations at Cambridge. 
nation, at an elevation of about thirty-eight and a half feet above 
the mean high-water mark of Charles River, at Brighton Bridge. 
These Observations have not been corrected for capillarity or 
elevation, but only for temperature. The correction for tempera- 
ture, which was derived from Professor Schumacher’s Tables, as 
published in the Report of the Committee of the Royal Society, 
reduces the observation to the standard of 32° Fahrenheit. Pre- 
vious to each observation, the mercury in the cistern was adjusted 
to the proper level. Observations made at different times by 
Mr. Bond show that the instrumental error of this barometer, as 
compared with No. 57 of Newman, described on page 3 of a for- 
mer paper, is .068 of an inch. The difference between this and 
038 of an inch, the capillary correction, or .03 of an inch, must 
be added to Cary’s instrument, when corrected for capillarity, to 
make it correspond with Newman. The Cambridge standard by 
Newman has already been compared with the standard of the 
Royal Society of London, as may be seen on the page just re- 
ferred to. 
Thus, the mean of all the barometric observations is 29.881 
Adding for the capillary correction, 0.38 
we have 29.919 
Adding difference between Cary and Newman, or -030 
we have 29.949 
Now we have, as the mean of four daily observations 
on Newman, during the same period of time as that to 
which our own observations refer, by Mr. Bond, 29.937 
Difference, .012 
If we deduct this last difference from .030 we have .018 as the 
value of the correction to reduce Cary to Newman, and which 
we prefer to the former correction of .030 of an inch, because it 
