72 
rOPULAR SCIENCE REVIEW. 
tion are most in vogue, sucli as opera-glasses and optical toys, 
the British collection is as showy, and, we believe, much more 
solid than those of other countries. It is interesting to notice 
the most ordinary applications of science ; how some dozens of 
spectacle-glasses are ground and polished at the same time — 
arranged and fixed around a convex or concave disc, — and how 
a rough lump of steel is punched and worked, until, without 
joint or soldering, it comes forth a spider-web frame for those 
lenses, such as Ariel might give, or Cinderella receive. In the 
higher branches of optical art, where the brain is equally 
potent with the fingers, we miss man} r names familiar in 1851. 
Merz, of Munich, who gained the council medal at the last 
Exhibition, is not represented in the present building, although, 
from the fine collection of telescopes which he is now construct- 
ing, he might easily have spared a specimen. Ertel, to whom, 
for his fine graduations, the jury awarded the great medal in 
1851, but who, nevertheless, by a decision of the council of 
chairmen, only received the ordinary one, is equally invisible. 
Troughton and Simms, to whom the same thing happened, are 
also unrepresented ; and the names of Lerebours, Secretan, 
and Steinheil, do not appear in the catalogue. Only one 
specimen of Foucault’s mirrors, and this of small dimensions, 
appears at the present international show. The United States, 
which, on the last occasion, contributed so much that was new 
and interesting — methods of recording transits, electric tele- 
graph apparatus, photographs of the moon — do not send a 
single article to classes 13, 14, or 15, and yet the excellence 
of Alvan Clarke’s telescopes is duly appreciated in this country. 
Neither the large telescope of Professor Amici (Florence), of 
1 7 ^-q inches aperture, nor any other of the splendid list of his 
scientific instruments given in the catalogue, arrived, although 
they had been eagerly expected, at the International Exhibition. 
Still, however, enough has been exhibited to show the pro- 
gress of science during the last ten years. The large equa- 
torial made by Grubb, of Dublin, strikes us by the solidity and 
convenience of its fittings ; the diameter of the object-glass is 
twelve inches, and, should it be worthy of the mounting, will 
certainly make a noble instrument. The mere metal-work is, 
however, a subsidiary affair in a telescope — what is most 
required is perfect and colourless definition, and this is only to 
be attained by the purity of the glass and the accurate form 
and complete polish which the artist bestows upon the four 
spherical surfaces of the crown and flint lenses. The finish of 
Cooke’s instruments is well known. His principal one is a tele- 
scope of eight inches aperture, equatorial^ mounted and furnished 
with a very solid base. The conveniences for motion in right ascen- 
sion and declination are excellent; the hour circle is moved by 
