4 H. C. RUSSELL. 
observatory labours Sir George Airy’s ever active mind produced. 
an endless stream of contributions to the furtherance of science. 
So early as 1857, he gave an oral statement to a meeting of the 
Royal Astronomical Society on the means which would be avail- 
‘able for correcting the Sun’s distance—one of the fundamental 
‘factors in astronomy, during the following twenty-five years. He 
repeatedly engaged in experiments in mines and on mountains to 
determine the density of the earth. He devoted a great deal of 
time to the reduction of tidal cbservations and published a masterly 
treatise on tides and waves. He undertook the printing of the 
account of the verification and extension of Lacailles are of the 
meridian by Sir Thomas Maclear, and edited many other works, 
and with Prof. Struve determined a great arc of the meridian, 
from the Ural River to Valencia. | 
In 1845 Mr. Airy was appointed one of three members of a 
Royal Commission to test the merits of railway gauges then in 
use, the report embraced the whole question, and the difficulties 
of break of gauge were duly considered, and finally after acknow- 
ledging that in some respects the broad gauge was to be preferred, 
recommended that as the majority of railways had adopted the 
narrow gauge, it alone should be maintained and permitted in all 
railways then under construction or hereafter to be constructed 
in Great Britain, and the transfer of the Great Western Railway 
trafic in this year to the narrow gauge is a striking comment on 
the wisdom of the report of the Royal Commission. He was 
Chairman of the Commission appointed to consider the general 
question of Standards, and of the Commission intrusted with the 
superintendance of the new standards of weight and length, after 
the great fire which destroyed the Houses of Parliament in 1834, 
To the testing and improvement of Marine Chronometers Sir 
George devoted a great deal of time and with most beneficial results 
to the accuracy of navigation. He contributed more than two 
hundred valuable papers to the Royal Astronomical Society and 
numerous contributions to other societies and publications, and 
published several books, perhaps the best known is that founded 
