TRANSACTIONS OF SECTION A. 917 
has been determined. To give constant light the height of the flame must be in- 
creased or diminished by ‘2 m.m. for every ‘1 inch of barometric height below or 
above 30 inches. The height of the flame is thus inversely proportional to the 
atmospheric pressure, as though the flame were a visible cone of gas of constant 
base. It is found that the height of the flame varies directly with the volume of 
gas passing to the burner. Recent observations on Ben Nevis show a less rate of 
variation for a difference of 4 inches of the barometer. 
3. On a Photometer made with Translucent Prisms. By J. Jouy, BE. 
When two pieces of a translucent substance such as paraffin are placed in con- 
tact along a plane face and illuminated by sources of light placed on opposite sides 
ofthis plane and viewed in this plane, they do not appear equally bright unless 
the illumination by each source is equal. This may be used as a very sensitive 
test of equality of illumination, and so as a photometer. It has this advantage 
over both shadow and Bunsen’s photometers, that the illuminated surfaces to be 
compared are in absolute contact along the line of contact of the two pieces of 
parattin. 
4, Report of the Committee for reducing and tabulating the Tidal Observa- 
tions in the English Channel, made with the Dover Tide-gauge ; and for 
connecting them with Observations made on the French coast.—See Re- 
ports, p. 60. 
5. Seventeenth Report of the Committee on Underground Temperature. 
See Reports, p. 93. 
6. Fifth Report of the Comivittee on Meteoric Dust.—See Reports, p. 34. 
7. A Tabular Statement of the Dates at which, and the Localities where, 
Pumice or Volcanic Dust was seen in the Indian Ocean in 1883-84. 
By Cuartes Metprvum, F.f.S.—See Reports, p. 773. 
8. Report of the Committee for co-operating with the Meteorological Society 
of the Mauritius in their proposed publication of Daily Synoptic Charts 
of the Indian Ocean from the Year 1861.—See Reports, p. 60. 
9. Daily Synoptic Charts of the Indian Ocean. 
By Cuartes Mexprvw, F.R.S. 
10. Report of the Committee appointed to co-operate with the Scottish 
Meteorological Society in making Meteorological Observations on Ben 
Nevis.—See Reports, p. 90. 
11. On the Meteorology of Ben Nevis. By AupxaNDER Bucwan. 
The advantages possessed by Ben Nevis as a first-class meteorological observa~ 
tory are these: itis the highest mountain in the British Islands, rising to 4,406 feet ; 
its summit is in horizontal distance little more than four miles from a sea level 
station at Fort William, and it is situated in the track of Atlantic storms which 
exercise so preponderating an influence on the weather of Europe, especially in 
autumn and winter. Its advantages are thus unique, and observations made there 
are of the highest interest and value in meteorology. 
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