1872.] Light. 527 
4. “On Buckholz’s System of Decorticating Grain, and making Semolina 
and Flour by means of Fluted Metal Rollers,” by Mr. W. Proctor 
Baker. 
Tron and Steel Institute——The fourth Provincial Meeting of the Iron and 
Steel Ins:itute was held this year in Glasgow, at the beginning of August 
last, under the presidency of Mr. Henry Bessemer. In his Address the 
President dwelt upon the various centres of iron manufacture which the 
Institute had successively visited, and the special branches of the manufacture 
for which each had become famous. The following papers were then read 
and discussed :— 
tr. On the Geological Survey, and the Geological Position of the Coal 
and Ironstone Strata on the West of Scotland,” by Mr. James 
Geikie, F.R.S.E. 
2. “*On the Rise and Progress of the Iron Manufa@ture in Scotland,” by 
Mr. John Mayer. 
3 and 4. ‘‘On Reversing Arrangements for Rolling-Mills,” by Mr. Graham 
Stevenson and Mr. R. D. Napier. 
5. ‘*A new Miners’ Safety-Lamp, for Indicating by Sound the Presence of 
Explosive Mixtures of Gas and Air, based on a new form of Singing 
Flame.” by Dr. A. K. Irvine. 
6. ‘*On the Rise and Progress of Iron Steam Ship-Building on the Clyde,” 
by Mr. D. Rowan. 
7. ‘*On Lauth’s System of Rolling Iron by Three-High Rolls,” by Mr. 
Lauth, of Pittsburg, United States. 
8. “On Further Improvements in Spencer’s Rotary Puddling Furnace,” by 
Mr. Adam Spencer. 
LIGHT. 
An alcoholic solution of fuchsine introduced into a hollow prism produces a 
highly anomalous spectrum, which, instead of proceeding regularly from the 
red to the violet, like the ordinary solar spectrum, stops at a certain point, 
returns backward, then stops again, and resumes a direct course to the end. 
Drs. Zéllner and Vogel have succeeded in measuring the velocity of the 
sun’s rotation by means of the spectroscope. The value obtained for the 
motion of a point on the sun’s equator is 0°42 German mile per second from 
one series of observations, and 035 mile from asecond. This new applica- 
tion of the spectroscope visibly recording the sun’s rotation will develope great 
interest, and we are sorry that the method of observation cannot be given 
shortly. 
Prof. Young has observed some peculiar phenomena relating to vision whilst 
pursuing a series of experiments. He writes as follows :—‘ In the course of 
some experiments with a new double-plate Holtz machine, belonging to the 
college, I have come upon a very curious phenomenon, which I do not re- 
member ever to have seen noticed. The machine gives easily intense Leyden- 
jar sparks, from 7 inches to g inches in length, and of dazzling brilliance. 
When, in a darkened room, the eye 1s screened from the direct light of the 
spark, the illumination produced is sufficient to render everything in the 
apartment perfectly visible ; and what is remarkable, every conspicuous objec 
is seen twice at least, with an interval of a trifle less than one quarter of a 
second—the first time vividly, the second time faintly ; often it is seen a third, 
and sometimes, but only with great difficulty, a fourth time. ‘lhe appearance 
is precisely as if the object had been suddenly illuminated by a light, at first 
bright, but rapidly fading to extinction, and as if, while the illumination lasted, 
the observer were winking as fast as possible. I see it best by setting up, in 
front of the machine, at a distance of 8 or Io feet, a white screen having upon 
it a black cross, with arms about 3 feet long and 1 foot wide, made of strips 
of cambric. That the phenomenon is really subjective, and not due to a suc- 
cession of sparks, is easily shown by swinging the screen from side to side. 
The black cross, at all the periods of visibility, occupies the same place, and 
is apparently stationary. The same is true of a stroboscopic disc in rapid 
