126 Scientific Intelligence. 
dertaken with the probability of its being completed without delay. It 
pers » ~ secon some day, ne" the sooner it is taken in haw 
western vate of New Granada, saahpeuann of the isthmus, wou 
imm 
rocks, which gradually pass from one to the other, and run in large 
layers, more or less, in a northerly direction. The schistose rocks are 
largely developed in the Boqueron end the Cascajal, te the laminated 
structure of the hornblendic rocks i is well defined, their inclination vary- 
beecominenh aeenecients are visible in the mass, and 
to numerou s black, green, piney white, brown, and bright red. 
_ From sa - =i, ha chain to the west, the mass is hornblendic, but 
Ghinct to the usual variations in its cat alternating between por 
phyry, greenstone, and basalt, conformably to the changes in the relative 
proportions of hornblende and feldspar. ‘There is a great soto 
lica in these rocks; quartz in spit 2 veins, or masses, is ake a , Hie 
Sprypnsitan ap are numerous, pad consis the penal super rior masses 
of the isth 
This sort t of spherical . exoliating decomposition, Sti scarcely a 
vestige of the original rock is percep common enough in. 
ene and porphyries ef the. yer and | che ete are 1 frequently 
| with a species of efflorescence of black ferruginous sand; 
and when this is sucerous the gold is found mixed wit th fr iron the 
course of time, the pieces scale, and the masses crumble ; . na being 
carried by rey dur to the cavities and Nelloea:. sec condary 
deposits are formed of ma eda), sand, Pie papi or gravel, 
which, i in ager warm mclimats are soon’consolidated in 
ad peso wn of Panama is situated on sec mene agilaceous sapeetes 
the original compound, to form a cement for binding together the s 
mentary deposits. Lime for building is a marine prgdoction, obtai ned 
principally from shells ; and, in consequence xcess of phos: 
and the absence of silicate of lime, and owe. i 
wee 
aes 
