164 
SCIENCE. 
in soft rock on the sides of hills — the apertures small and 
in some cases showing grooves for the adjustment of slabs 
of rock or other material to close them. The absence of 
remains in these caves could be explained from the fact 
that in earlier times outlaws and refugees often used them 
as places of shelter and residence, and laws had finally- 
been passed by the governors of some of the districts 
causing the caves to be filled up, or their entrances ob- 
structed, to prevent their being used in this manner. 
THE IRON ORES OF THE BRANDON PERIOD* 
By Henry Carroll Lewis. 
The theory that a great portion of the iron ores of our 
lower Silurian limestone valleys are of a tertiary age was 
first proposed by Prof. E. Hitchkock, but has been rejected 
by many geologists. The present paper describes in full 
recent discoveries, made by the writer, of lignite associated 
with limonite iron ores in the limestone valley of Mont- 
gomery County, Penn., and shows their relation to the 
deposit at Brandon, Vt., and their bearing upon a theory 
of the age of iron ores in similar positions in the Atlantic 
States. The lignite of Brandon, lying within beds of 
plastic clay, kaolin and iron ore, was shown by Lesquereaux 
to be of tertiary age. Lesley afterwards described strata of 
lignite in a similar position at Chambersburg, Penn., but 
regarded them as local deposits of late date. More recently 
Prime has found lignite in a plastic clay at Ironton, Penn., 
and supposed it to have been transported by a glacier. 
The present paper shows that in each of these cases the 
lignite lies far below the surface drift, and that, as at Bran- 
don, the latter lies unconformably upon the plastic clays 
containing the lignite. 
The occurrence of lignite in connection with limonite 
iron ore, plastic clay, kaolin and firesand in a number of 
places in Montgomery County, Penn., is described, and it 
is shown that these localities lie in a line corresponding to 
the line of strike of all the iron ores of the valley. Over- 
lying the plastic clay which contains the lignite is what ap- 
pears to be a decomposed lower Silurian hydromica slate, 
and for this reason the iron ores had been supposed to be 
of primal age. It is shown that this decomposed material 
and the underlying iron ores have been originally derived 
fromjower Silurian slates, and have been re-stratified in an 
age intermediate between Triassic and Upper Tertiary. 
The iron ores of this region may be divided into four 
classes : (t) Gneissic Ore ; (2) Primal Ore ; (3) Tertiary 
(Brandon) Ore ; (4) Drift Ore. The last two classes of ore 
are often found at the same locality ; the latter lying uncon- 
formably upon the former. The paper discusses at length 
the age of the drifts containing the latter. Notwithstand- 
ing the fact that a region of triassic red shale lies north and 
east of the valley, not a single fragment of such rock occurs 
in this drift. The pebbles are composed almost wholly of 
Potsdam sandstone, — a material now in great part eroded 
away in this vicinity. The evidence is strong that this 
drift was not caused by any flood from the north. That it 
is older than the Glacial Epoch is also shown both by the 
great amount of erosion it has suffered, and by the fact that 
in the adjoining triassic region no trace of drift occurs. It 
seems to have been formed at a time when hills of Potsdam 
sandstone, since eroded, stood as a barrrier between the 
limestone valley and the triassic rocks to the north. It is 
of interest to find that the pebbles of the sub-cretaceous 
clays of New Jersey are also formed of Potsdam. The 
four gravels of different ages of the Delaware valley are de- 
scribed, and it is shown that the drift ore of the Montgomery 
County valley belongs to the oldest of these, and is of 
Tertiary age. 
It follows that the strata containing iron ore and lignite, 
which underlie unconformably to this drift, are yet older. 
Some facts point to a Wealden age, but the identity of the 
deposits with that at Brandon, in which Tertiary plants are 
found, indicates a middle Tertiary, perhaps Oligocene age. 
Since an exact geological age cannot at present be assigned 
to these deposits, it is thought best to group them together 
under the name of the Brandon Period. 
Attention was directed to another deposit of lignite and 
iron ore near Augusta, Ga., recently found by N. A. 
Bibikov. Its geological situation and the section given is 
remarkably similar to those of Brandon, Chambersburg, 
Ironton and ihe Montgomery County Valley, and with 
them indicates the existence of a great inland fresh-water 
formation of Eastern America, during the Brandon Period, 
once fifty miles broad and nearly a thousand miles long. 
AMERICAN SOCIETY OF MECHANICAL ENGI- 
NEERS. 
We have received the first publication of this Society, 
which was organized on the 7th of April last. The objects 
of this Society are to promote the Arts and Sciences con- 
nected with Engineering and Mechanical construction, by 
means of meetings for social intercourse and the reading 
and discussion of professional papers, and to circulate, by 
means of publications, the information thus obtained. 
Mechanical, civil, military, mining, metallurgical and 
naval engineers and architects may be candidates for mem- 
bership to this Society, the initiation fee of members and 
associates being $15 and their dues $10 — payable in advance. 
The first President is Professor Robert R. Thurston, of 
the Stevens Institute, Hoboken. The Society starts with 
two life members — Thomas A. Edison, of Menlo Park, and 
George H. Norman, of Boston, and 189 ordinary members 
of different grades. We wish this Society success, and 
shall chronicle the work it performs. Those who desire to 
become members should address Lycurgus B. Moore, 96 
Fulton street. New York city. 
PHYSICAL NOTES. 
The beautiful proof that a constant current of electricity 
flowing through a thin gold plate can be deflected by a magnet, 
was exhibited by E. H. Hall on the 28th of last October, at 
Johns Hopkins University, and already we see how fruitful 
it is in suggestion to other scientists. Bolzmann, in a paper 
read before the Academy of Sciences in Vienna, calls atten- 
tion to the fact that is possible to calculate the absolute ve- 
locity with which the electricity flows through the gold plate, 
and gives a formula. 
A. von Ettinghausen also verifies Hall’s observations and 
deductions, in a thorough article containing plates of origi- 
nal apparatus. (Carl’s Reportorium.Vol. xvi., No 9, p.574.) 
Dr. Hall himself, in the September number of American 
Journal of Science , gives another paper on the subject, 
with detail of additional experiments, in which, besides 
gold, he uses silver, platinum, iron, nickel and tin, as thin 
conductors. For further information on this most instructive 
and interesting subject references should be made to the 
above-mentioned articles. 
It may be convenient to scientists who have had dealings 
with the late firm of Hall & Benjamin, of 191 Greenwich 
street, New York, one of the largest dealers in chemical 
and physical apparatus in this country, to know that J. & 
H. Bcrge, of 95 John Street, New York, have purchased 
everything appertaining to that business. 
The old friends of Mr. Hall will be glad to learn that he 
remains in the business, and maybe communicated with as 
before. 
The catalogue of these united firms has been placed be- 
fore us, and shows the magnitude of the business they con- 
duct, and the great facilities they offer scientific men in the 
production of every kind of philosophical apparatus. This 
catalogue is a handsome volume of over 200 pages, illus- 
trated throughout, and we advise chemists and physicists 
to apply for a copy. 
* Read before the A. A. A. S., Boston, 1880. 
