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Mineralogy and Geology. 127 
is great serge in ohaiaine a good composition for works exposed to 
the action of water, or _ ydraulic lime. ven to make lime for ordinary 
bind. The foregoing secondary deposits~-those of Barbacoas— 
white argillaceous deposits eranenes Cruces and E] Pequeui ts. Caimi- 
tello, are all the secondary rocks I have seen. There are a few calcareo- 
Siwuinian rocks, ie RNP Te vi mien erie ant St. Juan, 
i correctly speaking, they are not deserving of not The. je 
the shores of the Atlantic, on ‘ikewies the Saidionaninn is 
sian exclusively from the coral rocks, which so nonrne and ex- 
uberantly vegetate on the hornblendic shore of Portobello, > town 
and fortifications of Portobello are entirely built of cotal, and they appear 
very durable. The persons who have hinted at the existence of lime- 
stone and freestone quarries, in the Isthmus of Panama, must have been 
mistaken, and were evidently unacquainted with the geological position 
of these rocks. | ‘The question will now naturally arise—where are we 
to procur generals for a road in a paay where there is so absolute 
eesti articles ?. because, in case of either im- 
of th 
proving oe oe mode of transit, by means of an ordinary road, or 
making a road for 
4 
-and atceun. in both cases it will be requisite to 
prepare the localities intende 1 for the areepuon of cattle and cons strne- 
= bridges. . » 
vel, or hard and rongh s tor es, can be obtained from the pa 
convey any part, , and w 
economy than by the {ap see It I al be necessary to mak e the 
bridges high and wide over the Gatun and the Chagres, which how 
be effected by means of timber, judiciously Sale with wrought-i 
constructing them on the principle of obra de legadura—the pecker <a 
which, including the road and quay (mvelle) of Panama, will be forth- 
coming in due time, together with an approximative calculation of the 
cost. In case the gir gaa line should not be determined on for the or- 
dinary road cutting, and tructing dykes and bridges, the “inane 
of a carriage-road over a. nes rte would be trifling. In reality a ag 
executed, it is. a “toasible re ra construct a “rabiped ¥ joao c 
from the ear of Limon along the eastern bank of the Chagos te 
