March 23, 1894. 
female having placed all her eggs on the sides of the cage, 
it was decided to terminate the experiment. 
As a result I had fifty-two males, all attracted to a 
single female, in a locality in which the species is not 
more than ordinarily common. All arrived in the latter 
half of the night, indicating either that the sense of smell 
in the males is extraordinarily acute, and that they travel 
long distances to find the female, or else that it is their 
habit to be abroad only after midnight. JI have no very 
reliable data upon which to base a conclusion on these 
points. The scent glands of the female are to be looked 
for on the under side of the abdomen, where such organs 
have already been discovered in certain smaller members 
“of the same family of moths. The male organs of smell 
are doubtless the conspicuously branched antenne. 
IS GRANITE EVER METAMORPHIC? 
BY C. CALLAWAY, D.SC., F.G.S., WELLINGTON,: SALOP, 
ENGLAND. 
Ir is not so many years since it was commonly believed 
that granite was frequently of metamorphic origin. 
Numerous cases were quoted of a gradual passage between 
sedimentary strata and granite; and, as it was held to. be 
incredible that a sediment could be produced from granite, 
it was inferred that the granite was an aitered form of 
the sediment. The present writer shared in the popular 
belief, and in several papers written on the more ancient 
of the Archzan rocks of Great Britain, he assumed that 
the granitic masses called ‘‘ Dimetian ’ and ‘‘ Malvernian” 
were metamorphosed stratified rocks. But scepticism 
soon began to creep in. Case after case broke down on 
examination, until, within the area of the British Islands, 
he was unable to find a genuine case of a passage between 
a sediment and a granite. A few examples will here be 
given. : 
In North Wales, several cases were alleged. At Twt 
Hill, in the town of Caernarvon, granite was said to pass 
into a quartzose conglomerate. The gradations did indeed 
appear to be perfect in the field, but the microscope 
proved that the naked eye was not a reliable guide. It 
- was shown that the granite passed into the con-glomerate 
through the intermediate form of arkose, and even the 
authors of the metamorphic theory voluntarily surrendered 
it. A second locality was in central Anglesey. Here a 
band of granite strikes across the island, trending in the 
same direction as the adjacent sedimentary and schistose 
rocks. On one side of it lies halleflinta, passing into 
schist. The granite has been described as ‘‘ Dimetian,”’ 
and the hialleflinta as a younger formation called ‘‘ Ar- 
yonian.”’ The writer has given prolonged attention to 
these rocks, and has discovered localities where the 
granite is seen to send veins into the hialleflinta. The 
granite must, therefore, be of less antiquity than the 
halleflinta, and of eruptive origin. In other parts of 
Anglesey, certain sediments of Ordovician age have been 
supposed to be here and there converted into granite; but 
the most recent investigation of these rocks does not 
confirm this hypothesis. 
In England the facts are similar. The schistose and 
gneissic rocks of the Malvern Hills have been described 
as metamorphic Cambrian strata. Ata later period they 
were referred to the Laurentian system, being still 
regarded as altered sediments. The present writer has 
been studying these rocks for several years, and has 
described them as exclusively of igneous origin. The 
oldest varieties are diorites, and into these there have 
been intruded granites, felsites, dolerites, and other 
diorites. Subsequently to consolidation, these masses 
SCHEIN CE: 
157 
have been subjected to enormous pressures, which have 
produced shear-zones, in which the eruptive rocks have 
been converted into various gneisses and schists. A very 
good summary of the writer’s papers on these rocks has 
recently (February 9, 1894) been given in Science by 
Prof. J. W. Redway. Some of the conclusions are still 
under discussion; but the eruptive origin of the diorites 
and granites has been admitted by all those who have 
reviewed the work in the field. 
The Hebridean gneisses of Scotland have recently been 
examined by the Geological Survey of Great Britain. 
The conclusion of the Director-General (Sir A. Geikie) is 
that ‘‘after a most careful search in these rocks, not a 
vestige have we yet found of any unquestionable sedi- 
mentary material.” The writer has given some attention 
to alleged examples of metamorphic granite in Ireland. 
In County Donegal a great mass of granite rises amidst 
quartzites, limestones, and schists, and it has been 
affirmed that there is a gradual passage between the 
schists and the granite. The writer examined the junc- 
tion of the two kinds of rock on both sides of the granite 
mass, and found the clearest proof of igneous intrusion. 
At some points the granite veins are seen to run into 
schists, and to branch in the ordinary manner. Else- 
where the granite is in contact with limestone, and has 
altered it, producing in it an abundance of garnets as well 
as some lime-augites. 
In western Galway there is another alleged case of the 
passage of sedimentary rocks into granite. These, also, 
the present writer has examined. He has found clear 
evidence of breaks between the sediments and the schists 
into which they were supposed to pass. He has also 
ascertained that the» ‘‘metamorphosed conglomerates ” 
adduced in proof of the sedimentary character of the 
Galway schists are mixtures of schist, granite and diorite, 
or of two of them. A foliated structure sometimes ap- 
pearing in the granite was seen to be due to regional 
pressure, and not to sedimentation. 
A third case, occurring south of Wexford, was also 
investigated. The writer came to the conclusion that the 
granite of the Carnsore district nowhere passed into 
crystalline schists, and that the schists were sharply 
separated from the sedimentaries by faults. It is possible 
that some of the schists have been formed from igneous 
rocks, but, if so, they belong to a different period from 
the Carnsore granite, which shows no signs of foliation. 
In adducing these examples the writer infers no conclu- 
sion wider than the facts. He does not deny that there 
may be such a thing as metamorphic granite; he merely 
points out that certain alleged proofs have broken down 
on examination. Nevertheless, the results of the most 
recent work by other geologists have tended to confirm 
his investigations, and to suggest extreme caution in 
accepting other supposed cases of a passage between 
granite and stratified rocks. 
One cause of error in the past has been the assumption 
that a banded structure was always the result of sediment- 
ation. This view is now exploded, and need not be 
dwelt upon here. It has recently been shown that even 
rocks with all the appearance of a banded grit may be of 
igneous origin. The writer has described a very interest- 
ing case of this kind in the Malvern Hills. A granitoid 
diorite is crushed and decomposed. The hornblende 
passes into chlorite and iron oxide, which are inter- 
laminated with finely comminuted feldspar. Both in the 
field and under the microscope the rock has the appear- 
ance of a true sediment. Yet it may be traced without a 
break into the diorite on one side and into a mica-gneiss 
on the other. In the old days this grit would probably 
have been regarded as a conclusive proof that the whole 
series was of sedimentary origin. 
