174 REPORT—1890. 
The Committee greatly regret that they have to record the deaths of 
Sir J. H. Lefroy and of Professor 8. J. Perry, who have done very valu- 
able work for this Committee, and who have greatly advanced our 
knowledge of the subject of terrestrial magnetism. 
Report of the Committee, consisting of Professor Crum Brown 
(Secretary), Mr. Mitnu-Home, Dr. Jonn Murray, Lord McLaren, 
Dr. Bucuan, and the Hon. RatpH ABERCROMBY (Chairman), ap- 
pointed for the purpose of co-operating with the Scottish 
Meteorological Society in making Meteorological Observations 
on Ben Nevis. 
Dorine the past year the hourly observations, by night as well as by 
day, at the Ben Nevis Observatory, have been made by Mr. Omond and 
the assistants without interruption ; and the five daily observations at the 
sea-level station at Fort William have been also made by Mr. Livingstone 
with the greatest regularity. 
Again the state of the health of the observers, owing to the cireum- 
stance that active exercise in the open air is practically precluded during 
most of the year, rendered it necessary to give them relief during the 
winter and spring months. This relief the directors of the observatory 
were the better able to give through the courtesy of the following gentle- 
men, who gave their services as observers for periods varying from four 
to six weeks:—Mr. Alexander Drysdale, M.A., B.Sc., Mr. Charles E. 
Gray, Mr. James McDonald, M.A., Mr. R. C. Mossman, and Mr. Robert 
Turnbull, B.Sc. During the time Messrs. Omond and Rankin were in 
Edinburgh they gave much valuable help in the discussion of the Ben 
Nevis observations, and otherwise assisted in the work of the office of the 
Scottish Meteorological Society. 
Mr. Omond has completed an important investigation of the tempera- 
ture of Ben Nevis. From the six years’ observations he has calculated 
the mean temperature of each day of the year for the observatory at the 
top and for the low-level station at the foot of the mountain, and made a 
comparison of the two series of temperatures. The paper is in type, and 
will appear in the forthcoming ‘ Journal of the Scottish Meteorological 
Society.’ He has also re-examined the estimations of wind force and their 
equivalents in miles per hour from all the observations now available for 
the purpose, and the results are ready for publication in the same journal. 
Mr. Rankin has carried on, as the time at his disposal from his 
regular duties at the observatory permits, the work of photographing 
clouds and other meteorological phenomena. 
In the autumn of last year a grant of 501. was obtained from the 
Government Research Fund for carrying on an investigation into the 
numbers of dust particles in the atmosphere, by means of two sets of 
apparatus invented by Mr. Aitken, one being permanently fixed in the 
tower of the observatory, the other being a portable form of the instru- 
ment. Mr. Aitken superintended the construction of both instruments, 
and the placing of them with the necessary precautions at the top of the 
mountain. Reference will be made further on to the remarkable results 
obtained by the observations Mr. Rankin has already made. 
Messrs. Omond and Rankin are still engaged with the laborious 
