C. 8. Hastings—Spectra of the Limb and Center of the Sun. 369 
st Crystalline siliceous limestone, containing magnesia, .... 110 
5.) Blue clay, shale, and himpontenGsics. cies a 250 
my Maypeum, shale, and salty iis: cuies 06 coe e deus. ein cas 50 
i te ee 100 
Total depth, 1135 
The drilling done in this well was unprecedented in the 
annals of this system of mining, both for speed and absence of 
mishaps. Actual boring commenced on the 10th of March, 
1870, and the salt-bearing stratum was reached on the eve of 
the 22d of the same month. After passing through 100 feet of 
pure rock salt, without the least evidence of change, the boring 
was abandoned. The great success attending this boring led to 
the sinking of two other wells, viz: 
Sparling and Merchant’s, in the immediate vicinity; both, 
however, giving records similar to the above. 
Truly in no other portion of the American continent has 
there been discovered a deposit of salt so magnificently great. 
€ supply is practically illimitable, and may favorably com- 
pare with the production of the salt mines of Droitwich, in Cen- 
tal England, or with that of the solid salt-hills of Cordova. 
In a future paper I shall take occasion to describe the different 
systems of manufacture at present pursued in Western Ontario. 
—— 
Arr, XLIL— Comparison of the Spectra of the Limb and of the 
Center of the Sun, made at the Sheffield Scientific School; by 
Cuas. S. Hasrrnes. 
A COMPARISON of the spectrum of the edge of the sun with 
that of its center is of great theoretical interest ; but any compari- 
Son other than by direct juxtaposition must be very unsatisfac- 
tory, and the more so as the differences are less, In order to ob- 
tain spectra of two different portions of the sun side by side, where 
the slightest variations may be detected, I have constructed a 
small prism with four polished sides, its bases being parallelo- 
grams, This is so placed that one face rests upon the slit plate 
- the telespectroscope, and has its acute edge perpendicular to 
the slit at its middle point. The instrument-may then be di- 
rected so that the image of the sun falls with its center on the 
"Neovered portion of the slit, while the light which forms the 
se of the sun, falling perpendicularly upon the first surface of 
the Prism, suffers two interior total reflections and a displace- 
ment depending upon the form of the prism. A glance at the 
