250 
Mr. Spence drew the attention of the society to the great 
importance of the question of the action of acid water, 
especially in this district, upon boilers ; he employs the 
water from the Rochdale Canal in his boilers, and unless he 
were regularly to use soda to neutralise the acid, his boilers 
would undergo constant corrosion. By the addition of one 
pound and a half of soda per diem to each boiler, the plates 
were found to remain perfectly uninjured. 
Mr. Nasmyth communicated the following letter he had 
received from E. J. Stone, M.A., First Assistant at the 
Royal Observatory, Greenwich : — 
“ Royal Observatory, Greenwich, 
“ London, Feb. 25, 1864, 
“ Dear Sir, 
“ The Astronomer Royal has placed your letter of the 20th 
February in my hands. 
“Your discovery of the 1 willow leaves’ on the solar- 
photosphere having been brought forward at one of the late 
meetings of the Royal Astronomical Society, my attention 
was attracted to the subject. At my request the Astronomer 
Royal ordered of Mr. J. Simms a reflecting eyepiece for our 
great equatorial. The eyepiece was completed about the end 
of January last, and at the first good opportunity I turned 
the telescope on the sun. I may state that my impression 
was, and it appears to have been the impression of several of 
the assistants here, that the willow leaves stood out dark 
against the luminous photosphere. On looking at the sun 
I was at once struck with the apparent resolvability of its 
mottled appearance. The whole disc, so far as I examined, 
appeared to be covered over with relatively bright rice-like 
particles, and the mottled appearance seemed to be produced 
by the interlacing of these particles. I could not observe any 
particular arrangement of the particles, but they appeared to 
be more numerous in some parts than in others, I have used 
