IN THE HALL OF THE ROYAL SOCIETY. 
549 
column has been assumed to be in the ratio of the volume at 40° to the vo¬ 
lume at the observed temperature. To the correction thus obtained has been 
added, or from it has been deducted, the expansion or contraction of the brass 
scale on either side of the standard temperature 60°. 
Table of Corrections for Temperature for the Mercurial Barometer. Standard 
Temperature of Scale 60°. Volume of Mercury at 40° Standard. 
Tempe¬ 
rature. 
Inches. 
28* 
Inches. 
28-5 
Inches. 
29- 
Inches. 
29-5 
Inches. 
30- 
Inches. 
30-5 
35 
+ •007 
+ •008 
+ •008 
+ •008 
+ •008 
+ •008 
40 
— •005 
— •006 
—•006 
—•006 
— •006 
-•006 
45 
-•018 
—•018 
-•018 
— •018 
-•019 
-•019 
50 
— •030 
—•031 
— •032 
— •032 
— •033 
— •033 
55 
— •043 
— •043 
-•044 
— •045 
-•046 
— •046 
60 
— "056 
— •057 
— •058 
-•059 
— •060 
—•061 
65 
-•069 
— •070 
—•071 
— •072 
-•074 
— •075 
70 
— •081 
-•082 
— •084 
— •085 
— •087 
— •088 
75 
-•094 
-•096 
-•097 
-•099 
— •101 
— •102 
The mercurial barometer, with which the following- comparison has been 
made, is of a portable construction, and has been fully described on a former 
occasion*. It is the first to which a platinum guard was ever applied, and it 
still remains perfectly free from' air. The correction of +‘044 for capillary 
action has been experimentally verified, upon more than one occasion, by com¬ 
parison with a barometer of half an inch bore, in which no such correction is 
necessary. 
I have not hitherto had it in my power to institute such a series of observa¬ 
tions as I think the interest of the subject would have justified; as I have been 
obliged to depend upon my own exertions, or of those who from pure love of 
science have been willing to assist me in this laborious drudgery, at such in¬ 
tervals as the pressure of other engagements would permit. Of these by far 
the most important are the hourly observations of Mr. Hudson, which, with the 
assistance of some members of his family, he had the resolution to persevere in 
for fifteen days, and which he has communicated to the Society. Prior to 
these, were the following observations made at my request by Mr. Roberton 
in the months of August and September 1830, at different hours of the day; 
* Daniell’s Meteorological Essays and Observations, 2nd edition- 
MDCCCXXXII. 4 B 
