2l6 



SCIENCE 



[Vol. XXI. No. 533 



SCIENCE: 



Published by N. D. C. HODGES, 874 Broadway, New York. 



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EVIDENCE OF TWO PRE-MORAINIC GLACIAL MOVE- 

 MENTS. ' 



BY G. D. SWEZEY, DOANE COLLEGE, CRETE, NEBRASKA. 



The valley of Rock River, running southward through southern 

 Wisconsin and northern Illinois, is a very deep pre glacial erosion 

 gorge, cut through Lower Silurian rocks and filled with assorted, 

 incoherent glacial sands and gravels. Artesian wells go down sev- 

 eral hundred feet through these gravels before striking rook. The 

 region lies to the south of the great terminal moraine. 



Along the bluffs of this valley, at various points, there is ex- 

 posed a conglomerate, composed also of glacial gravels; it is a 

 pudding stone, thoroughly indurated, so as to make an excellent 

 rock for cellar- walls and the like; in some cases it is cemented 

 together by a calcareous matrix, in other cases there is a large 

 percentage of iron hydroxide in the cementing material. 



I have long known some of these outcrops, and have been puzzled 

 by them; but have supposed that they were due to local causes 

 afifecting the gravels which everywhere fill the broad valley; but 

 some more careful observations this summer reveal these facts : 



1. They rise, in every case that I have observed, ten to twenty 

 feet above the river bottoms. 



2. They are overlaid in some cases by the boulder-clay, con- 

 taining unassorted, striated pebbles. 



3. They occur, so far as I can discover, and lam pretty familiar 

 with the region, which was my native county, only on the ex- 

 treme edge of the bluffs overlooking the broad river bottoms, or 

 on the bluffs of valleys of some width which were tributaries to 

 the main valley when its latest bottoms were formed. They ap- 

 pear, in other words, to be remnants of older gravels which once 

 filled the valley, but were mostly cut away by the floods which 

 deposited the later, unconsolidated gravels now filling the vallev 

 and constituting its flood-plain at a level of ten to twenty feet 

 below the top of the conglomerate. In one place the extreme 

 face of the bluff, immediately below an outcrop of the conglom- 

 erate, was made up of layers of the light-colored, incoherent 

 gravels, alternating with dark, iron-stained material, evidently 

 derived from the older conglomerate, which then formed the 

 bluffs against which the stream washed. 



This distinction of age is confirmed by the occurrence of the 

 ground moraine of the latest glacial movement in this region, 

 overlying the consolidated gravels. 



There is no decisive evidence that the interval between these 

 movements was one of great duration, but the striking contrast 

 in appearance between the loose gravels and the conglomerate 

 tends to impress one with the idea that the latter is relatively 

 very old. So striking is this appearance, that at one exposure 

 which I visited I found the owner of the field laboriously digging 

 up an outcropping mass of this conglomerate, somewhat harder 

 and redder than usual, under the supposition that it was a mete- 

 1 Paper read before tUe Nebraska Academy of Sciences, Dec. 27, 1893. 



orite, which he purposes to take in to Chicago next year for an 

 exhibit. 



A further consideration, which would seem to imply a consid- 

 erable interval between the two movements, is that the follow- 

 ing succession of events would seem called for to explain the 

 facts: — 



1. A glacial movement bringing the material of which the con- 

 glomerate is composed, and which includes about the usual pro- 

 portion of local and remote ingredients. 



2. A melting of the ice and floods, surpassing in extent those 

 ot the later epoch, for the conglomerate, as before stated, lies 

 regularly at a higher level than the later gravels. 



3. Another forward movement of the ice to account for the 

 ground moraine overlying the conglomerate; and 



4. Another melting of the ice to deposit the later gravels. 



SOME NOTES ON LIGHTHOUSE APPARATUS. 



BY J. KENWARD, C.E., F.S.A., BIRMINGHAM, ENGLAND. 



In 1851, the United States possessed four sea-lights on the 

 dioptric system. In 1891 the number was of sea-lights 138, of 

 harbor lights 526, in addition to about 100 of the small apparatus 

 called range-lenses and lens-lanterns. 



This magnificent progress in forty years reflects the highest 

 credit on the Government and on its nautical and engineering 

 officers. Under official auspices in 1851, a most exhaustive en- 

 quiry was promoted into the merits of the dioptric or refracting 

 system of lights of Augustin Fresnel in comparison with the 

 catoptric or reflecting system which it had begun to supersede. 

 The result having been ascertained to prove a sevenfold supe- 

 riority for the dioptric system, the government authorized the 

 lighting of the United States coast- line on an imposing scale, and 

 it has ever since taken a watchful ani intelligent interest in the 

 advancement of lighthouse science, and in the gradual provision 

 of the best forms of optical and mechanical apparatus. 



The steps of progress, indeed, in lighthouse design and con- 

 struction have been many and important. The first home of this 

 industry was in France, where the illustrious mathematician 

 and physicist to whose practical genius the lenticular system is 

 due, lived his short life, dying in 1837. The celebrated Tour de 

 Cordouan. at the mouth of the Garonne, was the first lighthouse 

 to receive the new installation of his lenses. The names of 

 Leonar Fresnel, brother of Augustin, of Soleil, Letourneau, 

 Lepaute, Sautter, Barbier, Degrand, Allard, Raynaud, Bourdelles, 

 Bernard, and others follow in brilliant succession in France, as 

 engineers, constructors, or contributors to the literature of the 

 subject; while in the United Kingdom the great family of the 

 Stevensons, Mr. James Chance, Dr. John Hopkinson, Sir James 

 Douglass and Mr. Wigham of Dublin, may be cited as equally 

 distinguished. 



Nor have the authorities of the United States, while availing 

 themselves fully of the labors and researches of all these experts, 

 been backward in adding American names to the list of honor. 

 To mention only three, General Alexander, Major George Elliot, 

 and Major D. P. Heap are worthy, in their special work, of the 

 country of such men of science as Professor Henry and Professor 

 Newcomb. 



It is particularly to Major Heap of New York that credit is 

 due not only in selecting the most novel and striking forms of 

 apparatus produced in Europe, but also in promoting the design 

 and construction in the States, of the lanterns, lamps, clockwork, 

 pedestals, etc, which are indispensable to it. Major Heap is the 

 author, too, of an excellent compilation on lighthouses. 



Let me glance at some of the past achievements and present 

 resources of lighthouse science. 



During the past ten or fifteen years the great extension of com- 

 merce, the opening of new ports, the multiplication of steam 

 vessels of all classes, and the striking acceleration of their speed, 

 have affected lighthouses and lightships in the three essential 

 points of number, power, and distinctiveness. The chief mara- 

 time countries of the world — the United States, Great Britain 

 and her colonies and dependencies, France, Holland, Italy, and 

 Denmiirk, have endowed their coasts with an imposing array of 



