Dr Martin Barry on Fibre. 393 
finition of the colours depending upon the interference of light 
falling on different parts of the drop, when the drop subtends 
a considerable angle, the interference becomes indistinct. 
The aid obtained by the use of the telescope in Dr Scores- 
by’s experiments does not, I apprehend, consist in magnify- 
ing the drop itself (p. 51, 55); and the most effectual focus 
would not be found to coincide with that which would give a 
distinct view of the drop. In the case of very minute drops 
only a feeble pencil of rays emerges truly parallel in any posi- 
tion; but a telescope adjusted so as to concentrate approxi- 
mately all the somewhat scattered rays which fall upon the 
object-glass will give a more regular spectrum, just as a spec- 
trum formed on a wall with a lens is better than one Regt 
has not been concentrated. 
Finally, Dr Scoresby attributes (p. 54, 55) the variation in 
the angle at which the spectral colours appear, to the observed 
want of sphericity of the dew-drops ; and he farther proposes 
to apply this to the explanation of supernumerary rainbows. 
It is only necessary to say that this view was long since pro- 
posed by Venturi (Report on Meteorology, p. 126), but has 
been generally abandoned since the discoveries of Dr Young. 
I am, my dear Sir, yours very truly, 
James D. Forzes. 
To Proressor JAMESON. 
Dr Martin Barry on Fibre. 
Martin Barry, M.D., read before the Royal Society of London, in 
December 1841 and January last, a memoir on Animal Fibre. In this me- 
moir the author observes, that, in the mature blood-corpuscle, there is often 
seen a flat filament, already formed within the corpuscle. In Mammalia, 
including Man, this filament is frequently annular ; sometimes the ring 
is divided at a certain part, and sometimes one extremity overlaps the 
other. This is still more the case in Birds, Amphibia, and Fishes, in 
which the filament is of such length as to constitute a coil. This filament 
is formed of the discs contained within the blood-corpuscle. In Mam- 
mals, the dises entering into its formation are so few as to form a single 
ring; and hence the biconcave form of the corpuscle in this class, and the 
frequent annular form of the filament it produces. In the other Verte- 
brata, the dises contained within the blood-corpuscle are too numerous 
