186 ANNUAL OF SCIENTIFIC DISCOVERT. 



giving the real light and shade that would be developed by the light 

 falling on the model at a suitable angle. The mountains have their 

 shadow-side engraved in the usual manner by "hachures" but the 

 light-side is only slightly tinted in parts, to develop detail of form, and 

 is brilliantly relieved by a tint spreading over the level plain like an 

 India-ink wash j this tint is made of several grades of strength, in- 

 tended to show the relative altitude of the several plateaus over which 

 it is spread, the lowest or alluvial lands having the darkest tint, and 

 the loftiest table-lands having the most delicate. 



The result in the present map is bold and striking, showing at a 

 glance the nature of the whole country, enabling any one to perceive 

 the character, prominence, and relation of the different parts. This 

 region of country has features unsurpassed in their kind for grandeur 

 and sublimity ; the Colorado of the West flowing for 300 miles of its 

 course through canons whose sides often rise perpendicularly from 

 3,000 to 6,000 feet in height ; while the " Great Canon of the Col- 

 orado " is the most magnificent gorge, as well as the grandest geologi- 

 cal section, of which we have any knowledge. For this region Eg- 

 loffstein's system of mapping has unquestionable advantages. Its 

 freedom from conventionality and truth to nature give it a power, 

 unattainable by the old system, of representing forms so that they 

 are intelligible to every eye. The French, at one time, used a sys- 

 tem of topography similar to this. It had light-sides and shade-sides 

 to the mountains, but they did not tint the level plains, on which so 

 much of the character and beauty of this style depends. 



M. FAYE ON SOLAR REPULSION. 



The following paper by the well-known French astronomer, M. 

 Faye, is translated from the Comptes Rendus, March, 1862 : 



It follows, from a consideration of all the facts relating to the ac- 



^j 



celeration of comets, and of the forms they assume, that there exists 

 in celestial space a repulsive force, exerted by the surface of the 

 sun ; that this force is due to incandescence, and operates like 

 attraction at all distances. The physical phenomena which surround 

 us afford striking indications of a force of this nature, and we can 

 put them in evidence by causing an incandescent surface to act under 

 the conditions which are revealed to us by the study of astronomical 

 effects. There is thus an identity between the two forces which 

 have their origin in heat, just as there is an identity between celes- 

 tial attraction and terrestrial attraction, as shown by the fall of 

 heavy bodies in the celebrated experiments of Maskeleyne and Cav- 

 endish. But repulsion exerted at a distance by an incandescent sur- 

 face cannot be a different thing from the molecular repulsion which 

 is equally due to heat, the force to which physicists attribute the 

 phenomena of dilatation, of changes in the state of bodies, and 

 their elasticity in the gaseous form. We arrive then at the conclu- 

 sion that there exists in nature a force not less general than attrac- 

 tion, and which, like attraction, manifests itself in celestial spaces, as 

 well as in molecular intervals. 



There is, however, a difficulty which seems to oppose this complete 

 identification. The molecular repulsion due to heat has always been 



