235 
or between rollers, could be continually pushed forward into 
a gas or spirit-lamp flame in which it would burn.” 
Professor Roscoe stated that great credit was due to Mr. 
Sondstadt for the able manner in which he had brought the 
difficult subject of the metallurgy of magnesium into the 
present satisfactory position, and expressed his opinion that, 
even for photographic purposes, the application of the metal 
will prove most important. Mr. Brothers, Mr. Parry, and 
other photographers present, corroborated Dr. Roscoe’s 
opinion respecting the value of such a source of light for 
photography. Since the meeting Mr. Brothers made an 
experiment upon the magnesium light, which he reports as 
follows ; — 
“ The result of an experiment I have just tried is that in 
50 seconds with the magnesium light I have obtained a good 
negative copy of an engraving — the copy being made in a 
darkened room. Another copy was made in the usual way in 
daylight, and in 50 seconds the result was about equal to the 
negative taken by the artificial light. The sun was shining, 
but there was a good deal of fog in the atmosphere.” 
A paper was read, entitled, On the Tensile Strength of 
Cotton,^ effected by various Chemical Treatments.” By 
Mr. Charles O’Neill, F.C.S. 
The author has given a great number of experiments upon 
the subject, made in order to elucidate some important practical 
and scientific points not hitherto much worked upon. By 
means of his apparatus for testing tensile strengths (Proceed- 
ings of this Society, No. 6, 1863-64, p. 186) he was enabled 
to obtain data which by any previously known method 
