96 JOURNAL OF SCIENCE, 
rate. Of course, the energy (ze. the capacity to do work) of the 
cannon ball will vary as the square of the velocity. 
Further on the author appears to prove that the force of 
gravity does more work in one unit of time than in another, and 
then that it does not, and finally sums up thus: “It will be seen 
therefore that the distance through which a body falls during the 
time of falling is not a measure of the work of the force of 
gravity during that time.” Of course not ; and we do not know 
that this is affirmed by anyone. During the third second, for 
example, a body falls through 80 feet, and of this only 16 feet is 
due to the force of gravity acting during that second—a fact 
well known to all physicists; but how this can mean “that the 
ordinary measure of the kinetic energy of a mass in motion is 
erroneous,” we cannot at all see. We presume the aptness of 
the title of the tract depends entirely upon this. = 
PGi 
CORRESPONDENCE. 
a 
(To the Editor N.Z, JOURNAL OF SCIENCE.) 
S1r,—During a visit to Auckland last December, I took the 
opportunity, by leave of Mr. T. F. Cheeseman, of re-examining 
the specimen of Voluta kirki (mihi) in the Museum, and came 
to the conclusion that it was V. flavicans (Gmelin), which is 
found at New Caledonia, &c. The specimen has been a very 
long time in the Museum collection, and has seen many changes 
in curators ; no doubt it has got by accident among the New 
Zealand shells, and really came from some of the Pacific Islands. 
The same may, I think, be said with reference to Witra obscura 
(mihi), Cyprewa punctata, Marginella vittata (mihi), and Raeta 
perspicua (mihi),all of which are founded on one or two dead speci- 
mens in the Colonial Museum, from the Bay of Islands. Conus 
Zealandicus (mihi), in the same collection, and from the same 
locality, is undoubtedly C. aplustre (Reeve), and I quite agree 
with Mr. Justice Gillies, that it cannot be considered as a New 
Zealand shell. I should put in the same category Adamsia 
typica, Fasctolaria trapezium, Risella melanostoma, Philippia 
lutea, and Thalotia conica. Great caution should be shown in 
admitting a species, common in other countries, into our list ; it 
should only be done when either living specimens have been 
obtained, or when dead shells have been found in such quanti- 
ties, and in such various places, as to exclude the possibility of 
their having been dropped. I myself, in company with Mr. C. 
Traile, once found on the beach at Maketu a specimen of JZztra 
episcopalis, but neither of us supposed that it was a New 
Zealand shell.—I am, &c., 
F. W. HUTTON, 
Christchurch, 16th February, 1882. 
J 
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