Ohituary Notices. 
Ixxv 
3. An elaborate inquiry, with numerous anemometers placed on 
poles at various heights, into the important question of the rate 
of diminution of the wind’s velocity with height. 
4. The proposal, in 1875, to obtain from High Level Stations 
and Observatories the data for determining “Vertical Gradients” 
for atmospheric pressure, temperature, and humidity, from their 
important bearing on meteorological questions generally, but more 
particularly on weather changes. Ben Nevis Observatory and 
High Level Observatories of other countries have now been for 
some time carrying on this great work in a degree and to an 
extent scarcely in contemplation when the proposal was made 
in 1875. 
The Council of the Society recorded in the Minutes of their 
meeting of July 11, 1887, their grateful testimony to the vigour 
and prudence with which Mr Stevenson discharged his duties as 
Honorary Secretary, and to his unfailing courtesy and readiness 
to aid and oblige oh all occasions. 
{SuiDNementary, by D. A. Stevenson, Esq.). 
In addition to what has- already been stated, should be men- 
tioned his design of a Bivalve apparatus in 1859; also the design 
and introduction, in 1886, of “Lightning Light” apparatus at the 
Isle of May electric light, both of which have been strongly 
advocated since by the engineers of the Erench Lighthouse Board. 
But, perhaps, the most notable improvement of recent times is his 
firm’s design of the Hyper-radiant apparatus. This apparatus was 
designed to take advantage of burners of increased diameter and 
initial power, and, when tried at the South Foreland in 1885, it was 
found to be greatly superior to the other lenses tried against it, 
and is now largely used at home and abroad. 
Along with his brother David he made experiments in 1870 
on the use of paraffin as a lighthouse illuminant, and after trial 
at Girdleness Lighthouse, they reported to the Commissioners of 
Northern Lighthouses that paraffin should be introduced into all 
the Scottish lighthouses, as its use would increase the intensity of 
the lights, while their maintenance would be greatly reduced. 
