83 
Single Mkroscopes of Glass. 
size than As the lenses thus formed sometimes contain 
air bubbles, the best way is to make several, and select those 
^vhich are freest from faults. An eye or loop, made by bending 
the exti'emity of a platinum wire, may be used instead of the 
platinum leaf. 
The reason for using platinum, is, that the glass is more easi- 
ly and more perfectly melted in this than in other metals, which 
may perhaps arise from its bdng a bad conductor of heat, and 
from its preserving its brightness. As platinum does not oxidate, 
the glass adheres better to the edges of the hole, and it may be 
used very thin, as it does not melt with the heat necessary for 
the complete fusion of the glass. 
Mr Sivright has likewise succeeded in forming, what, in so 
far as we know, was never attempted, plano-convex lenses by 
means of fusion. In order to do this, he took a plate of topaz, 
with a perfectly flat and polished natural surface, which is easily 
obtained by fracture ; and having laid a fragment of glass upon 
it, he exposed the whole to an intense heat. The upper sur- 
face of the glass assumed a spherical surface in virtue of the 
mutual attraction of its parts, and the lower surface became per- 
fectly flat and highly polished, from its contact with the smooth 
plate of topaz. 
Art. XVI. — Remarlcs on the Size of the Greenland Whale^ 
or Balsena Mysticetus, designed to show that this animal is 
found (f‘ as great dimensions in the present day as at any 
former period since the establishment f the whale-fishery 
By William Scoresby junior, F. R. S. Edin. and M. W. S« 
Communicated by the Author. 
Such is the avidity with which the human mind receives 
communications of the marvellous, and such the interest attach- 
ed to those researches which describe any remote and extraordi- 
nary production of nature, that the judgment of the traveller re- 
ceives a bias, vdiich, in all cases of doubt, induces him to fix 
upon that extreme point in his opinion which is calculated to af- 
ford the greatest surprise and interest. Hence, if he perceives^ 
® This paper was read before the Wcrnerkp Natural Society qI 
««ir"h, on the i9th of December 1818. 
F 3 
