12 
POPULAR SCIENCE REVIEW. 
placed in hot embers. This treatment drove off the mercury, 
and left a small, spongy hall of gold inside the clay coating. 
This process only extracted a portion of the free gold, as 
assays of their ‘ tailings 9 show 30 per cent only of the gold to 
have been extracted. 
North-east of Gualilan, and on the eastern side of the Sierra 
de Villagun, at the junction of the beds of the Rio Flanche 
and Rio Chilca, which carry water during the rainy season only, 
is situated a remarkable hit of country. The same limestone 
as that found in the Sierra Yillagun is crossed by the road, 
which then passes over barren hills of shale and sandstone to 
the edge of the Valley Fertil. In these hills, parallel to 
another limestone range in the distance, considerable deposits 
of bituminous shale are found. These shales vary in thick- 
ness, from six inches to eight feet, and are imbedded in 
yellowish grey shale. One deposit, eight feet thick, has been 
opened by natives in the hope of finding coal, and samples from 
the depth of 90 feet gave volatile matter and fixed carbon 9 ’6 
per cent, ash, 86 90 per cent. Colour black, lustre bright, and 
on exposure to the atmosphere the lumps break up into thin, 
shaly leaflets ; the ash of this shale contained gold and silver 
in all the samples examined, the highest quantity being 1J 
ounce of gold, and 1J ounce of silver per ton. The seams can 
be traced along the sides of the regularly stratified hills for a 
considerable distance (say two miles). Close to these seams are 
found deposits of ironstone, containing 45 per cent of that 
metal, and very nearly the same proportion of gold and silver 
as in the ash of the shale. This is a remarkable fact, and 
becomes still more so, when we find that the gossan from the 
decomposition of the pyrites in the limestone hills to the west 
contains the precious metals in almost the same proportion. 
There is a deposit of coal at ITilario, in this province, a 
sample of which gave 11 J per cent of ash. It is found in the 
sandstone and shaly beds there existing, and is of such a cha- 
racter as to lead to a well-founded hope of the people that they 
may have a coal of Oolitic age to assist in building up their 
mining and other industries, and in reducing the expenditure of 
their scanty store of timber. 
EXPLANATION OF PLATE I. 
Fig. 1. Diagrammatic section of rocks in the Gualilan district. 
Fig. 2. Section of pipe-vein, with granite forming foot-wall. 
Fig. 3. Primitive native mill for grinding gold ores. 
