P OP ULAR MIS CELL ANY 



859 



orological system; 2. The schistose rocks 

 of the eastern half, in Vermont, are to a 

 large extent similar to those of the western ; 

 3. The rocks of the central mountain sec- 

 tion in Vermont are, in its northern part, 

 identical schists with those on the east and 

 west sides of it ; 4. The western border of 

 the region in the Hudson River Valley has 

 its folded or upturned Hudson River (Low- 

 er Silurian) slates overlaid unconformably 

 by the Niagara and Lower Helderbcrg (Up- 

 per Silurian) beds ; 5. The eastern border 

 of the region in the Connecticut Valley at 

 Bernardston, in Massacliusetts, Vernon, in 

 Vermont, and the adjoining part of New 

 Hampshire, has Lower Helderberg beds 

 overlying, unconformably, folded or up- 

 turned roofing- slates (similar to those on 

 the western side), the Lower Silurian age 

 of which is not improbable ; and at Little- 

 ton, in New Hampshire, and on Lake Mem- 

 phremagog, in northern Vermont, occur 

 unconformable Upper Helderberg (Lower 

 Devonian) beds with fossils ; 6. A moun- 

 tain-individual of folded rocks — which is 

 defined as comprising all the elevations or 

 results of upturning or flexure that were 

 produced over a continuous region in one 

 mountain-making process — is necessarily 

 one of great magnitude. Professor Dana 

 does not consider his theory as established, 

 for a further study of the stratigraphy of 

 the eastern part of the region is required 

 for that, but he believes that the facts, 

 which he reviews in detail, are strongly in 

 its favor. 



Gas and tlie Electric Light.— The ques- 

 tion of the feasibility of substituting the 

 electric light for gas is yet far from settle- 

 ment. The competition will be finally de- 

 cided by the consideration of the relative 

 expense, regard being also given to the 

 quality of the light afforded. Some experi- 

 ments which have recently been made for 

 increasing the illuminating power of gas 

 have been attended with satisfactory re- 

 sults. The most effectual devices are those 

 by which a more perfect combustion is 

 secured. By concentrating a number of 

 burners so arranged as to play upon each 

 other, and by improved arrangements for 

 regulating and directing the draught of air 

 upon them, the amount of light has been 

 tripled, and it has been made clearer and 



more fixed. Burners constructed with this 

 object in view have been tried in London, 

 and found to give a considerable increase of 

 light at a less increase of expense. Other de- 

 vices, produced by French inventors, promise 

 well. The inventors of electric lights seek 

 either to produce single lights to supplement 

 the defective illumination given by ordinary 

 lights, or to divide the light, so as to make it 

 take the place of gas entirely. The appara- 

 tus devised by Messrs. Regnier and Werde- 

 mann and Mr. Edison, for the latter pur- 

 pose, give an agreeable light; but that is 

 only a part of the problem. The diificulty 

 of securing an economical production and 

 supply of electricity remains, and that equal- 

 ly whether we seek to distribute it so that 

 each consumer shall use only what he needs, 

 or to store it in reservoirs of force. Experi- 

 ments which have been made upon the 

 amount of light produced per horse-power 

 of motive force give greatly varying re- 

 sults. The light of M. Mersanne, with the 

 Lontin machine, is rated at 80 carcels ; the 

 Jablochkoff light, with the Gramme ma- 

 chine, at 38 carcels ; and Mr. Edison's ma- 

 chine, with 10 of his carbon lamps, at 15 

 carcels. A comparative trial of the strength 

 of the Jablochkoff and Mersanne lights and 

 gas was made in the latter part of Decem- 

 ber at one of the railway-stations in Paris. 

 Six of the Jablochkoff lights, ten compound 

 intensive gas-burners, and four Mersanne 

 lights, were used. The brilliancy of the 

 gas-light was to the Mersanne light as 1 to 

 5-6V, and to the Jablochkoff light as 1 to 

 r927. On direct comparison, the brilliancy 

 of the Jablochkoff was to the Mersanne as 

 1 to 3. Roughly, 6 Mersanne hghts were 

 equivalent to 1 8 Jablochkoffs and 34 gas-jets. 



Composition and Fses of Cellnloid. — Cel- 

 luloid, which has come into extensive use 

 in the arts, is a species of solidified collo- 

 dion, produced by dissolving gun-cotton in 

 camphor with the aid of heat and pressure. 

 From a description of its composition and 

 mode of manufacture by Dr. "W. H. Wahl, 

 we gatlier the following : The process of 

 preparing gun-cotton is well known ; by it 

 the properties of the vegetable fiber are so 

 changed that it becomes soluble in alcohol 

 and ether, as in making collodion, cam- 

 phor, and other substances. In the pro- 

 cess invented by the brothers Hyatt, gun- 



