216 The National Geographic Magazine 



The bulletin contains 60 brief papers, 

 of which the following may be men- 

 tioned : ' ' Investigation of Metalliferous 

 Ores, " by S. F. Emmons ; ' ' Placer Gold 

 Mining in Alaska in 1902," by Alfred H. 

 Brooks ; " Gold and Pyrite Deposits in 

 the Dahlonega District, Georgia," by 

 E. C. Eckel ; " Mineral Deposits of the 

 Bitterroot Range and the Clearwater 

 Mountains, Montana," by W. Lind- 

 gren ; ' ' Gold Mining in Central Wash- 

 ington," by George Otis Smith ; " Ore 

 Deposits of Tonopah and Neighboring 

 Districts, Nevada," by J. E. Spurr ; 

 " Ore Deposits of Butte, Montana," by 

 W. H. Weed ; " Lead, Zinc, and Fluor- 

 spar Deposits of Western Kentucky," 

 by E. O. Ulrich and W. S. T. Smith ; 

 " Coal Fields of the United States," by 

 C. Willard Hayes. 



GEOLOGICAL HISTORY OF NEW YORK 

 CITY 



THE geological history of New York 

 and its vicinity is discussed at 

 great length, illustrated by numerous 

 maps and pictures, in New York City 

 Geologic Folio, No. 83, recently issued 

 by the Geological Survey. 



Tens of thousands of years ago the 

 greater part of the State of New York 

 was covered b}' an immense glacier, 

 similar in character to those now found 

 in Switzerland and Alaska, but im- 

 mensely greater in area and thickness. 

 This ice sheet had gathered up in its 

 course large quantities of sand, gravel, 

 and mud. Part of this burden was 

 pushed before the ice mass, and as the 

 front of the glacier came to rest in the 

 latitude of the city, the material pushed 

 ahead of it was deposited there. When 

 the glacier disappeared, owing to the 

 coming on of a warmer climate, the 

 mass of material deposited along its 

 front became the familiar rounded hills 

 of Long Island — the so called backbone 

 of the island. 



After the disappearance of the ice 



sheet, the land in the vicinity of the 

 city sank, so that the sea covered 

 points now 100 feet above tide level. 

 During this period of submergence, the 

 great brick-clay beds along the Hudson 

 River were deposited. The traveler on 

 the Central or the West Shore road can 

 now see these beds — near Croton Land- 

 ing or Haverstraw, for example — far 

 above the railroad tracks, but the}' were 

 all formed under water. 



The next event in the history was, 

 on the contrary, a gradual rising of the 

 land until it stood considerably higher 

 than at present. This was followed by 

 a sinking just as gradual, which is still 

 in progress: Along the coast of Long 

 Island and New Jersey tree stumps may 

 be seen under water. It is known that 

 these have been covered by the sea 

 within very recent times, and that the 

 encroachment of the sea on the land is 

 still going on. 



Many other subjects of interest are dis- 

 cussed in this folio, which is the most in- 

 teresting contribution to New York local 

 geology ever published . It may be pur- 

 chased from the U.S. Geological Survey, 

 Washington, D. C, for 50 cents. 



The apparatus or box for developing 

 photographic films without the aid of the 

 dark-room, referred to in this Magazine 

 in May, 1902, will prove of great service 

 to explorers and travelers. The present 

 season is the first opportunity that men 

 in the field will have of using the ma- 

 chine, as it was placed on the market too 

 late last year. With the little box, 

 which is no larger and not so heavy as 

 a camera, one will be able to develop 

 one's films in the evening beside the 

 camp fire, or if a specially fine landscape 

 is seen which the traveler wishes to se- 

 cure beyond all doubt, he may develop 

 his snap-shot in broad daylight before 

 moving on, provided water is at hand. 

 The box, invented by Mr A. W. Mc- 

 Curdy, is known as the Kodak Develop- 

 ing Machine. 



