i6 4 



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 oie, 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 

 from lower 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 : (i) 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 arc 

 found, indicates a middle Tertiary, perhaps Oligoccne 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. 



* ReaU before the A. A. A. S., Boston, 1880. 



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 ot 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. Berge, 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. 



