140 REPOET — 1891. 



The variations of the field strength with pressure of the gas seem to 

 agree ■with the Grotthuss chain hypothesis as far as the measurements go. 



Upon the assumption that the passage of electricity from a point to a 

 plate is a one-way flow, it is possible to obtain a value of the ratio of 

 mass moving to electricity carried by it (i.e., the electro-chemical equiva- 

 lent of the discharged matter) in terms of the slopes of potential and 

 pressure brought about by the discharge, and the density of the current 

 passing. Experiments are now in j^rogress to determine this ratio, rf 

 possible. So far they point to a number far in excess of the electrolytic 

 value. This may be due to error in the measurements, or, possibly, to 

 the presence of metal dust in the discharge. 



Measurements, also still in progress, have been made on the mechan- 

 ical forces which act on a point during dischai'ge. They point to interest- 

 ing difiTerences between + and — electricity, and it is hoped that useful 

 information may be obtained as to the manner in which the two electri- 

 cities leave the point by further work in this direction. 



Tour Committee asks for reappointment with a grant of 50Z. 



Report of the Committee, consisting o/Lord McLaren (Chairman'}, 

 Professor Crum Brown {Secretary), Mr. Milne Home, Dr. John 

 Murray, Dr. Buchan, and the Hon. Ealph Abercromby, ap- 

 pointed for the purpose of co-operating with the Scottish 

 Meteorological Society in inahing Meteorological Observations 

 on Ben Nevis. 



Ddeing 1890 the hourly observations by night and by day at the Ben 

 Nevis Observatory have been carried on uninterruptedly by Mr. Omond 

 and the assistants, and as heretofore the five daily observations at Fort 

 William have been made with great regularity by Mr. Livingston. As 

 intimated in last report, a vitally important advance was made in the 

 system of observations on Ben Nevis by the opening of the low-level ob- 

 servatory in Fort William on July 14, 1890, for regular continuous obser- 

 vations. This observatory has been equipped by the Meteorological 

 Council Avith a complete set of self-recording instruments, such as are in 

 use at the first-class observatories of the Council. The directors have 

 thus now at their disposal the best information available for extending the 

 scientific and practical inquiries they have undertaken through the 

 unique facilities offered by these well-equipped observatories. A begin, 

 ning has also been made with an elaborate discussion of this double series 

 of hom-ly observations of which some account will be given in this 

 report. 



The directors were again able to give relief to the various members 

 of the observing staff by the courtesy of the following gentlemen, who 

 have given their services as observers for periods varying from four to 

 eight weeks: — Messrs. R. C. Mossman, James McDonald, M.A., and 

 Alexander Drysdale, M.A., B.Sc. ; and Messrs. P. Gillies and C. Stewart, 

 from Professor Tait's Laboratory, are now (August, 1891) assisting in 

 the work of observing. 



For the year 1890 the following were the monthly mean pressures and 

 temperatures, hours of sunshine, amounts of rainfall, and number of fair 



