928 REPORT—1885. 
isoclinals. The survey was begun in the summer of 1884, and was continued during 
the spring, summer, and autumn of the present year. We have been assisted in 
some of our later observations by Mr. A. P. Laurie, of King’s College, Cambridge, 
who was good enough to undertake the measurement of the dips at a number of 
the inland stations. Our best thanks are due to Mr. Laurie for the valuable help 
thus rendered. 
It is hardly possible for us as yet to say anything about the general results of 
the survey, as the observations are only partially reduced. We trust to be able to 
complete the calculations without delay. We venture, however, te hope that the 
statement that all the necessary observations for what now constitutes the third 
Magnetic Survey of Scotland have been taken, may not be without interest for the 
members of the British Association. 
TUESDAY, SEPTEMBER 15. 
The following Reports and Papers were read :— 
1. Report of the Oommittee for considering the best means of Comparing 
and Reducing Magnetic Observations.—See Reports, p. 65. 
2. Report of the Committee for considering the best methods of recording the 
direct Intensity of Solar Radiation—See Reports, p. 156. 
3. On a means of obtaining constant known Temperatures. 
By Professor W. Ramsay, Ph.D., and Sypney Youne, D.Se. 
This method, which has involved the determination of the true vapour-pressures 
of numerous substances, with help of mercurial, air, and vapour-pressure thermo- 
meters, is published in full in the ‘Trans. Chem. Soc., Sept., 1885. 
4. On certain facts in Thermodynamics. 
By Professor W. Ramsay, Ph.D., and Sypney Youne, D.Se. 
This paper has reference to the equation 
_L _@t 
s—s, dtJ 
L 
While Dr. Ramsay discovered in 1877 that at the same pressure is approxi- 
&—8, 
mately constant for all liquids for which there exist data, the correctness of the 
data and assumptions on which the statement is based was open to question. Hence 
the investigation was unpublished until a relation in some degree connected 
with this was rediscovered by Mr. Trouton, ‘ Phil. Mag.’ 1884, p. 54. Since then, 
Dr. Young noticed that the value of dp T at the same pressure is an approximate 
dt J 
constant for all liquids, and as the data in this case are much more reliable than in 
the former, it has been thought desirable to publish both researches under one title. 
The first law is:—The amounts of heat required to produce unit increase of 
volume in the passage from the liquid to the gaseous state at the boiling-point under 
== 88 
81-5. 
The second law is:—Zf the amounts of heat required to produce unit increase of 
volume in the passage from the liquid to the gaseous state be compared at different 
pressures for any two bodies, then the ratio of this amount at the boiling-point under 
normal pressure are approximately constant for all bodies ; or 
