48 SCIENCE. 
Bizzozero attributes the origin of thrombi in blood- 
vessels to the destruction of these corpuscles. He 
has been able to watch the process of formation in 
the mesenteric vessels of living animals when a lesion 
of the walls of the vessels was produced in any way. 
In the blood of animals with nucleated red cér- 
puscles, Hayem has described a form of corpuscle 
which has properties analogous to those possessed 
by the blood-plates of mammals. These gorpuscles 
may be preserved for study by the use of the liquids 
mentioned above. They are colorless, nucleated, 
slightly flattened bodies, bearing a general resem- 
blance in shape to the red corpuscles, though usually 
more elongated at one or both of the poles. They 
vary greatly in size, but as a rule are somewhat larger 
than the white corpuscles. They are distinguished 
from the white corpuscles mainly by a difference in 
form and by the changes which they undergo after 
the blood has been shed. The white corpuscles are 
' always more or less spherical, while the plates are 
flattened disks. After the blood has been shed, they 
‘become exceedingly viscous, and form granular 
masses from which fibrous processes radiate. Their 
functional value in coagulation appears to be the 
same as that of the blood-plates in mammals with 
non-nucleated red corpuscles. 
WILLIAM H. HOWELL. 
THE COMSTOCK LODE. 
Geology of the Comstock lode and the Washoe dis- 
trict. By Grorcr F. Becker. (Monographs 
U.S. geol. surv., ili., with an atlas.) Washing- 
ton, 1882. 422 p. 4°. 
THE appearance of the second of the new 
series of monographs published by the U.S. 
geological survey will be greeted with pleasure 
by the scientific world, not only on account 
of the amount of new information it contains 
regarding the geological and physical character 
of one of the most important ore-deposits on 
the globe, but also as an index of the increas- 
ing interest which is being taken in this coun- 
try in a very important but comparatively new 
branch of geological research. Becker’s report 
contains, with perhaps one exception, the most 
considerable contribution yet made by an Amer- 
ican to microscopical petrography, and deserves 
for this reason, aside from its other merits, high 
commendation. 
Referring, for a historical, economic, and 
technical treatment of the Comstock lode, to 
the works now in preparation by Messrs. 
Lord and Eckart, the author devotes himself 
to a purely scientific investigation of this inter- 
esting region. <A résumé of the results reached 
by von Richthofen, Zirkel, King, and Church, 
is given, which is followed by a detailed de- 
scription of the rocks in connection with which 
the ore-deposits occur. This work is carefully 
le te Te ara eae a, 
~ 
done, and, notwithstanding a very apparent 
‘lack of acquaintance with the literature and 
many important methods of modern petrogra- 
phy, is a valuable contribution to the subject. 
For instance: the actual presence of the sus- 
pected sodalite in the granite might easily have 
been placed beyond a doubt by a simple mi- 
crochemical test. 
extinction-angles would have been much more 
satisfactory had they been made on cleavage 
pieces from their isolated powder instead of in 
the sections; while Boricky’s test would cer- 
tainly have yielded as good results as Szabo’s. . 
The variety of rocks in the area studied is 
very great, comprising, in order of their ages, 
granite, metamorphics, granular diorite, por- 
phyritic diorite, metamorphic diorite, quartz- 
porphyry, earlier diabase, later diabase, earlier 
hornblende andesite, augite andesite, later horn- 
blende andesite, and basalt. None of these 
exhibit in their occurrence or structure any 
thing very striking or abnormal, if we except 
the sodalite in the granite, whose presence is, 
however, left very doubtful. Of especial inter- 
est are the decomposition processes, which 
have altered the rocks in the area between the 
Comstock and Occidental lodes almost past 
recognition. «These are thought to be due to 
solfataric action, which was not earlier than 
the eruption of the later hornblende andesite ; 
and they have received a good share of the 
author’s attention. All the rocks of this area 
are equally decomposed ; and, in the case of all, 
the same minerals have undergone the same 
alteration. Hornblende, augite, and mica 
change into chlorite, and this in turn gener- 
ally to epidote, though sometimes to a mixture 
of quartz, calcite, and limonite. The felspar 
becomes filled with secondary fluid inclusions, 
and finally forms a mass of calcite, quartz, 
and a substance of unknown character, which, 
according to the author, is certainly not kao- 
line. 
By far the most interesting results of the 
author’s studies, from a petrographical stand- 
point, are those arrived at in reference to the 
origin and nature of that much-discussed rock- 
type, propylite. As is well known, this name 
was given by von Richthofen to certain early 
tertiary, andesitic rocks of Hungary, possess- 
ing a fibrous green hornblendic constituent and 
a granitic habit. Both von Richthofen and Zir- 
kel regarded the Washoe district as a locality 
where this type was especially well developed ; _ 
and the present author entered upon his work 
fully convinced of the correctness of their 
views. All the more interesting, then, is the 
fact that a careful and elaborate study of these 
[Vou. IIL, No. 49. 
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