APRIL 16, 1914] 
NATURE 177 
of the eighteenth century, supposed the metallic con- 
stituents of veins to have been produced by the action 
on pre-existing stony and earthy matters of subter- 
ranean vapours arising from certain processes of 
‘fermentation ’”’ in the bowels of the earth. 
In 1749 Zimmermann put forward a- hypothesis 
which clearly had in it the germ of the modern theory 
of metasomatism. He ascribed the origin of veins 
to a transformation of the rocks into metallic minerals 
and their accompanying vein-stones, along certain 
directions now marked by the course of the veins, the 
solvents that effected the alteration finding a path 
through innumerable small rents and other openings 
in the rocks. 
But Zimmermann applied his theory indiscriminately 
to explain the origin of all veins, including those that, 
by common agreement, are now considered to have 
been formed by the filling of fissures without replace- 
ment. Von ‘Treba, in supporting Zimmermann’s 
view, insisted particularly on the far-reaching changes 
effected in rocks by circulating waters, especially 
when aided by heat. ‘‘I am persuaded,’ he wrote 
in 1785, ‘‘that there is constantly going on in our 
mountains a variety of transformations, compositions, 
and decompositions, which not only take place at 
present, but will continue to the end of time.” 
According to Gerhard, who wrote in 1781, waters 
circulating through the rocks adjacent to a vein 
become charged with certain of the metallic and earthy 
substances contained in them. Passing through the 
crevices and interstices of the rocks to the larger rents 
and fractures, they deposit their mineral burden in 
cavities which, when filled, become veins. It will be 
seen that Gerhard’s hypothesis must be regarded as a 
precursor of the more modern theory of lateral secre- 
tion. 
To von Oppel belongs the credit of having shown 
that mineral veins were largely the filling of fault- 
fissures, a principle which up to that time does not 
appear to have been clearly recognised. 
At the end of the eighteenth century the mining 
world was dominated in all matters relating to ore- 
genesis by the famous Freiberg professor, Abraham 
Gottlieb Werner, who insisted that all veins, includ- 
ing those that we now term. ‘‘intrusive dykes,’’ had 
resulted from the filling of contraction-fissures open 
above and connected with the primeval universal 
ocean, which according to the Wernerian doctrine 
covered the globe and contained in solution all the 
necessary materials for the formation of its crust. 
These waters, descending into the fissures from above, 
deposited the vein minerals by chemical precipitation. 
This Neptunist view was in the beginning of the 
nineteenth century attacked and finally overcome by 
Hutton and his Plutonist or Vulcanist school. Un- 
fortunately, however, the Plutonists went:to the other 
extreme, and would not allow even ore-veins to have 
any other than an igneous origin: ‘‘The materials,” 
wrote Playfair, ‘‘ which fill the mineral veins were 
melted by heat and forcibly injected into the clefts and 
fissures of the strata.” 
But Hutton’s broad generalisation, even with the 
important modifications of Elie de Beaumont, 
Daubrée, and Durocher to the effect that many of the 
metallic ores had been deposited from vapours and 
solutions. emanating from cooling igneous magmas, 
was soon discarded in favour of the deposition from 
waters of meteoric origin; and an animated discussion 
was maintained for half a century on. the respective 
merits of the descensionist, ascensionist and lateral 
secretionist theories; or, in other words, whether the 
mineral burden ot the circulating waters instrumental 
in vein-formati¢h was derived from superficial rocks, 
from deep-seated sources, or from the wall-rocks of 
the veins themselves. 
NO. 2320, VOL. 93] 
The chief supporters of the modified form of the 
ascension theory here alluded to, which must, of 
course, be distinguished from De Beaumont’s ascen- 
sion by emanation, were Stelzner and Posepny. They 
argued that the ground-water (originating by pre- 
cipitation from the atmosphere) descends by capillarity 
through the interstices of the rocks to deep-seated 
regions, and thus acquires a high temperature and 
pressure, and, consequently, a vastly increased solvent 
power, whereby in its passage through the rocks it 
is enabled to take up certain of the mineral sub- 
stances there disseminated in a minute form. At a 
certain depth the water moves laterally towards open 
conduits, on reaching which it ascends towards the 
surface, depositing its mineral burden in proportion 
to the decrease of temperature and pressure. 
It has been seen that the theory of lateral secretion, 
or the derivation of the mineral contents of veins by 
an aqueous leaching of the country rock, was ad- 
vanced in a crude form as early as 1781 by Gerhard; 
but it remained a mere hypothesis without the support 
of ascertained facts until the middle of the nineteenth 
century, when the chemical work of Bischof, Forch- 
hammer, and Sandberger definitely established two 
important facts in support of the theory, namely :— 
(1) That the gangue of ore-veins varies in correspond- 
ence with the wall-rock; and (2) that the heavy metals 
occur in minute traces in certain of the igneous and 
sedimentary rocks constituting the ‘‘ country ”’ of ore- 
veins. 
Sandberger’s researches were specially directed to 
prove that the heavy metals (gold, silver, copper, lead, 
etc.) are contained in the common ferro-magnesian 
silicates (namely, the micas, hornblendes, and augites) 
of the igneous rocks; and having satisfied himself on 
this point he was led to extend his investigations to 
the sedimentary rocks, with the result that small 
quantities of the heavy metals were found in the sedi- 
ments of all ages, and especially in the slates of the 
older systems. Whether, however, they are there pre- 
sent as constituents of sporadic fragments of ferro- 
magnesian silicates derived from igneous rocks, 
or as. sulphides that were introduced during 
the secondary mineralisation connected with  ore- 
deposition, was not satisfactorily settled by Sand- 
berger’s researches. The more recent work of Don, 
carried out on a great variety of material, tends to 
show that the ferro-magnesian silicates do not carry 
gold or silver in amounts determinable by chemical 
analysis. Where the rocks examined by him were 
found to contain these metals they were present as a 
constituent of sulphides, such as iron pyrites, pyrrho- 
tite, mispickel, chalcopyrite, and galena, which in most 
cases are secondary introductions. 
But long before this the inapplicability of lateral 
secretion: as Sandberger conceived it had become 
apparent; and the theory became the subject of vigor- 
ous attack on the part of Stelzner and Posepny. 
Lateral secretion, in a much more extended sense 
and in combination with the ascension theory, is advo- 
cated by Van Hise. Van Hise’s view may be briefly 
summarised thus: the meteoric waters, after pene- 
trating the surface, are widely scattered through the 
rocks in innumerable small openings as they travel 
downward to great depths in the earth’s crust. With 
steadily increasine temperature and pressure they take 
up mineral matter. The -downward movement ulti- 
mately develops a lateral component, by: which the 
waters are carried to the larger openings. During 
this process, also, the waters continue to take material 
into solution. In the larger openings the waters 
ascend with decreasing temperature and:-pressure, and 
there the ores are deposited. 
It will be seen that this view is a combination of 
the ascension and the lateral secretion theories, and 
