OCTOBER 22, 1897. ] 
as the typical camptonite in the Pemigewassett 
Valley, N. H. 
By diligent investigation it was my good 
fortune last August to discover in the locality 
of these ramifying dikes and the famous Cor- 
inth copper mines an extraordinary dike of 
limburgite, from 6. to 10 feet in width, and 
penetrating the calciferous mica schist toward 
the west for more than half a mile. 
This limburgite bears individual crystals of 
olivine two to three inches in length and 
one to two inches in breadth. A single speci- 
men has been placed in the museum of Dart- 
mouth College containing a crystal of olivine 
two and one-half inches by one and three- 
fourths. 
Some of the smaller crystals by the oxidation 
of the iron have become converted into limo- 
nite or hematite; others have gone over into 
serpentine, while a bit of calcite derived from 
the contiguous orthorhombic pyroxene or the 
basic plagioclase feldspar is occasionally seen 
in the cavities once filled by the original olivine 
crystals. f 
As the locality is to the northward in the 
exact direction of the moving ice, and at a dis- 
tance of only about twenty miles from the 
famous Thetford boulders, it seems evident that 
Corinth, Vt., was their original habitat. 
C. H. RICHARDSON. 
DARTMOUTH COLLEGE. 
MORE DICTIONARY ZOOLOGY. 
SOME time ago I called attention in your col- 
umns to the inaccurate zoological information 
given by a recently published dictionary. I 
have just had occasion to examine the Encyclo- 
pedic Dictionary (Philadelphia, 1896) and 
should like to ask how the editors explain the 
following eccentricities : 
(1.) Snail. “‘ H. aspera is also eaten.’’ Helix aspersu is 
the snail intended ; H. aspera is a totally dif- 
ferent snail, found in the West Indies. 
(2.) Slug. ‘A. agrestis, the Red Slug.’? There is 
no Arion agrestis, ‘The article, with its errors, 
appears to have been taken ( without ac- 
knowledgments) from an old edition of Cham- 
bers’ Encyclopedia. Tf the editors had exam- 
ined the recent edition of that standard work, 
published several years before 1896, they would 
haye found a different account. 
SCIENCE. 
633: 
(3.) Coccus. The species assigned to Coccus belong 
to seven perfectly distinet genera ; and no au- 
thor in the last twenty-five years who has 
given any study to these insects has used the 
last century classification of the Encyclopedic 
Dictionary. 
The editors of dictionaries will have to real- 
ize that if their zoological definitions and arti- 
cles are to be accurate and up-to-date they 
must employ specialists to write or revise them. 
Until they do so, zoologists should make it their 
business to call attention to the misrepresenta- 
tion of their science in works which the public 
is asked to receive as models of accuracy. 
T. D. A. CoCKERELL. 
SEPTEMBER 25, 1897. 
LANTERN TRANSPARENCIES. 
To THE EDITOR OF SCIENCE: Those who have 
occasion to have copies of engravings or pic- 
tures of any kind made for use with the lantern 
may be glad to know that such may be printed 
from the plates used in ordinary printing if 
sheets of thin transparent celluloid be taken. 
Gelatin also may be used. The latter is liable 
to roll up more or less and needs to be protected 
by inclosing between glass plates of the ordi- 
nary size for lantern slides. Celluloid will not 
trouble so much in that way, yet it is best to 
mount such pictures in the same way. Photo- 
graphic half-tones show very well indeed, 
the fine meshing not being enough magnified 
nor dense enough to be noticed upon the screen 
at the distance of a few feet. Such copies need 
cost but a few cents apiece if the electro can be 
got to print from, and if celluloid be used with- 
out the glass cover perhaps one cent would be 
the full cost. I enclose a couple of samples 
that you may judge of the quality of such pic- 
tures. 
A. EK. DOLBEAR. 
DANGERS OF FORMALIN. 
To THE Epiror oF ScreNcE: Now that the 
use of formalin for preserving objects for dissec- 
tion is becoming so common, I think a word of 
warning as to the danger involved in the use of 
even attenuated solutions should be given. It 
is doubtless a matter for the medical faculty to 
