J. L. Smith—Incrustation of Aragonite. 107 
I have made experiments on several different specimens, and 
the results vary little from each other. The range of temper- 
ature with which the experiments were made was from zero 
to ., on a bar 25mm. in diameter, and 304 mm. long, 
this expanding in length 9-10 mm.; making the entire ex- 
pansion equal to ;4,; of the entire length of the rod for a 
temperature ranging from freezing to boiling point, giving as 
coefficient for linear expansion for one degree centigrade 
0000079365. This coefficient is seen to be lower than that of 
mercury ; but from the fact that mercury corrects the pendu- 
lum by only one-half its expansion, and the vuleanite is made 
to correct it by its entire expansion, the length of vulcanite re- 
quired is even jess than the column of mercury used in the mer- 
curial pendulum. This instrument is one whose use depends 
on its accuracy of operation after careful trial for some time. 
ART. XU —Aragonite on the surface of a meteorite iron, and a 
new mineral (Daubréelite) in the concretions of the interior of the 
same ; by J. LAWRENCE SmitH, Louisville, Ky. 
L Incrustation of Aragonite. 
THE remarks in this communication have reference to some of 
the masses of iron that have been brought from that region of 
Mexico called the Bolson de Mapini, or the Mexican desert, sit- 
uated in Cohahuila and Chihuahua, two of the northern prov- 
Inces of Mexico; the desert being four hundred miles from 
fast to west, and five hundred miles from north to south, border- 
img on the Rio Grande. This region, so prolific in masses of 
Meteoric iron, has been described by Prof. Burckhardt of Bonn 
self. 
(this Journ., Noy., 1869); and in 1871 I was enabied to give a 
s-cription and an analysis of a still larger one weighing about 
00 kilograms, this last one remaining on the western bound- 
ary of the desert near El Para. 
e have some account of one even larger than the last, 
ia in the very center of the desert. So far as known there 
posh been found in this locality not less than 15,000 kilogra 
br one matter, an amount exceeding that which has po 
Tought together in cabinets from all other sources. 
