1822.] Scientific Intelligence. 311 
examined by Don Josef Rodriguez, director of the Observatory of 
Madrid, and one of the most eminent disciples of the school of Freyberg. 
According to the geometric levelling of Don Clemente Rojas, the 
Picacho de Veleta is elevated 3,447 metres, or 11,309 feet above the 
sea: and the altitude of the Cerro de Mulhacen is 3,531 metres, or 
11,585 feet. 
The formations which constitute the entire mass of these mountains 
are primitive, and have great uniformity. They are mica-slates, which 
pass into gneiss and clay-state (phyllade, thonschiefer) ; and which 
contain subordinate beds of eupholite (serpentine, diallage rock), of 
quartz, and probably also of greenstone (diabase). There is neither 
granite nor true gneiss; nor are the fragments of those rocks found 
even in the neighbouring alluvial tracts. The existence of greenstone 
in subordinate beds is rendered extremely probable by the blocks of 
that substance which are dispersed around the principal chain. In 
this greenstone crystallized garnets are disseminated, as in that of the 
mica-slates collected by Humboldt in the chain of the littoral of Ca- 
racas. On the southern declivity of the Sierra Nevada, clay-slate re- 
poses on the mica-state, and supports, in its turn, black transition 
limestones rich in sulphuret of lead. 
It might appear from the abundance of the beds of greenstone, that 
the whole mass of these mountains belongs to the transition formation ; 
but it must not be forgotten that the stanniferous granites of the 
Fichtelgebirge in Franconia also present beds and veins of greenstone, 
and that M. de Buch has discovered primitive eupholites in the North 
of Europe.* The strata of rocks which compose the Sierra Nevada 
are inclined in the form of tiles ; that is to say, their direction is nearly 
parallel to that of the central chain, and they dip towards the north 
on the northern declivity, and towards the south on the southern. In 
the Alps, the strata are most frequently inclined towards the centre 
of the chain; on the coast of Italy they dip to the north. It will be 
interesting to the geognost to be well acquainted with the relation of the 
volcanic rocks of Cap de Gates to the intermediary and primitive for- 
mations of the Sierra Nevada. The tract which surrounds this chain 
is so elevated, that the upper platform of the tower of the Cathedral of 
Grenada is itself 784 metres, or 2,572 feet, above the marine level, 
(Ann. de Chim. &c, xx. p. 99.) 
III. On the Preparation of Formic Acid from Tartaric Acid. 
Professor Dobereiner has found that when bitartrate of potash, or 
pure tartaric acid, is slightly heated with black oxide of manganese and 
water, a great quantity of carbonic acid escapes, and a sour colourless 
liquid distils, which is formie acid. 
1, It is, evenat the common temperature of the atmosphere, decom- 
posed by concentrated sulphuric acid into oxide of carbon and water. 
2. By nitrate of silver and pernitrate of mercury, when slightly 
_ heated, it is completely converted into carbonic acid, while the oxides 
are reduced to a metallic state. 
* It may be added, that diallage-rock and serpentine occur associated with gneiss, 
mica-slate, and other primitive rocks, in the Shetland Isles ; and that the latter is also 
found in detached beds and masses in the granite of Aberdeenshire. There does not, 
indeed, appear to be any reason for supposing that the rocks of the Sierra above noticed 
belong to the transition class.x—Ep. 
