S16 Mr Galbraith oil a Table for correcting the SutCs Altitude'^' 
Some of the newer secondary rocks may have been formed 
from the water of cold-springs alone, collected into hollows, and 
thus forming lakes ; or from hot-springs in the same circum- 
stances; or from both conjoined. The newer secondary, more 
properly tertiary, formations of limestone, marl, opal, quartz,: 
&c. may have been formed in this way. 
General Results, 
From the preceding rapid sketch it appears, , 
1. That the water of springs and of volcanoes forms rocks of 
various descriptions, some of which nearly resemble those of the 
Volcanic class, while others have a strong resemblance to the for- 
iflations of the secondary class. 
2. That as these springs and volcanoes are very generally 
distributed over the earth, it folfows that the rocks above de- 
scribedj may occur in very considerable abundance, and form 
striking and extensive features in the physiognomy of some 
tracts of country. 
Q, That many of these rocks, from their close resemblance to 
Volcanic productions, may have been confounded with them. 
4. That the following rocks and simple minerals have been,, 
and are still forming by the agency of springs, and the water of 
volcanoes : 
1* Rocks resembling Trap cmd Volcanic Rocks, — Basalt,- 
Wacke, Amygdaloid, Tuffa, Porphyry, Greenstone, Ob- 
sidian, and various clays and boles. 
2. Rocks resembling Floetz or Secondary Rocks, — Traverti-’ 
no, Calcareous-tuffa, Calcareous-sinter, and Marl. 
S. Simple Minerals,^ — Pearl-sinter, and probably also Pre- 
cious Opal, Common Opal, and Jaspers of various de- 
scriptions. 
Art. XVIII. — Description and Use of a Table for Correcting 
the observed Altitude of the Sun^s Lower Limb, By Mr W. 
Galbraith. In a Letter to Dr Brewster. 
Having seen a very neat and commodious Table of Propor- 
tional Logarithms in the last Number of the Edinburgh Philo- 
sophical Journal, I conjectured that you meant to convey to the 
public, through that medium, useful tables, when they fall in 
