i879-1 
Notes. 
207 
a durability greater than that which would be required for night 
operations in England ; and the third is absolute steadiness, to 
enable work to be conducted without affedting the eyes. There 
is no electric light that has yet been introduced which supplies 
us with these desiderata. 
The first of the Friday evening discourses, at the Royal Insti- 
tution of Great Britain, was given on the 17th ult., by Professor 
Tyndall, his subjedt being “ The Eledtric Light.” The eledtric 
light had, he said, been known for seventy years, as in 1808, and 
again in an improved form in 1810, it was shown to audiences at 
the Royal Institution. Prof. Tyndall quoted Faraday’s saying, 
that he would rather occupy himsejf with finding fresh effedts 
than spend his time in exalting those effedts. But it was the 
exaltation of these effedts which he first studied in a simple way 
which has led to the present possibilities of our eledtric lighting. 
Prof. Tyndall gave a historical sketch of the various arrange- 
ments, beginningwith that of Mr. Holmes in 1862. The different 
“ candles ” in use were also described. Prof. Tyndall said he 
did not believe any fresh scientific discovery was needed to make 
the eledtric light of general application to large places. The 
scientific man knew what different natures of machines were 
required to do the different kinds of work to be done. It re- 
mained now for mechanical skill to carry out the work. In 
conclusion he pointed out the mistake of those who, like Cuvier, 
spoke with contempt of those whose practical skill carried to 
utility the experiments of the philosopher. 
The Philosophical Society of Glasgow have instituted a 
triennial ledture in memory of the late Prof. Graham, Master of 
the Mint. The Council have also caused a portrait medal of the 
value of £10 to be struck, and this they propose to award every 
third year for the best original investigation, either in chemical 
physics or in pure or applied chemistry, which maybe communi- 
cated to the Society or to its chemical sedtion in the interval of 
the awards. The choice as first Graham Ledturer appropriately 
fell on Mr. W. Chandler Roberts, F.R.S., who had so long been 
associated with Graham’s work, and who was enabled to employ 
much of his original apparatus. The ledture was given on the 
22nd ult., Mr. James Young, F.R.S., presiding. Mr. Roberts 
described in detail the experiments that enabled Graham to 
establish the law of the diffusion of gases, and he illustrated 
experimentally the passage of gases through porous bodies, 
such as unglazed earthenware arid artificial graphite, as well as 
through a layer of the hard translucent variety of opal known as 
hydrophane. Mr. Roberts pointed out that the Graham law of dif- 
usion forms the basis of the science of molecular mechanics, and his 
measurements of the rates of diffusion prove to be the measure of 
molecular velocities which have been investigated mathematically 
by Clerk Maxwell, Clausius, and Boltzmann, and experimentally 
by Losehmidt in developing the dynamical theory of gases. 
