4.24) Dr. Bigsby's Sketch of the Topography 



the sphere of the heavens, for instance, if one hemisphere be 

 projected on the same plane, the form of the configurations of 

 the stars is entirely lost, and the map ceases to bear any re- 

 semblance to the appearance presented to the eye. This 

 would not be the case if the sphere were projected upon six 

 planes forming the sides of a cube, the eye being supposed at 

 the centre. The distortion at the corners would be too tri- 

 fling to interfere sensibly with the effect to be produced. The 

 heavenly sphere would thus be contained in six maps, which 

 would have the advantage of enabling any one to find any 

 star or constellation with the greatest readiness. If the pole 

 be taken for the centre of the upper surface of the cube, and 

 the maps be divided by meridians and parallels of declination, 

 the sides of the cube are symmetrical, the parallels of declina- 

 tion are portions of hyperbolas, and the meridians are straight 

 lines ; the upper and lower surfaces are also symmetrical, the 

 parallels of declination are circles, and the meridians are 

 straight lines. 



LXIII. A Sketch of the Topography and Geology of Lake On- 

 tario. By J. J. BiGSBY, M.D. F.L. and G.S., For. Mem. 

 Amer. Phil. Soc. ^c. 



[Concluded from p. 347.] 



T"^HE next place at which I have met with conglomerate is 

 -*• seven miles above this strait, close to a well-marked bluff 

 promontory. Here the cement is in great quantity ; and is 

 clay, coloured by chlorite : the quartz nodules are often red, 

 and are both rounded and angular. It is at the water's edge. 

 Some hundred yards below the deposit of schorl on Mr. Mac- 

 kenzie's farm before spoken of, elevated strata of milky quartz- 

 rock make their appearance on the beach, accompanied by 

 the granular gneiss, containing schorl and chlorite. Resting 

 in close contact on the quartz is a coarse conglomerate of the 

 same materials, in a green cement ; and above it is an hori- 

 zontal brown limestone, full of quartz nodules at the bottom 

 of the ledge, but which, gradually diminishing in number and 

 size, disappear almost wholly in the upper layers. This very 

 coarse conglomerate of milky quartz forms a ledge fifteen feet 

 hio-h, about three hundred yards south-west of the same de- 

 posit of schorl, close to a creek on Mr. Mackenzie's farm, and 

 is ao-ain filled with fragments of the last-named mineral. It 

 is in this case surrounded by debris and soil, and therefore is, 

 as far as we can observe, unconnected with any rock. These 

 puddingstones seem to be merely local deposits, thick and ex- 

 tensive as we have seen them to be ; for on the shores of the 



outlet 



