Geology and Mineralogy. 315 
disastrous effects became somewhat increased in the mountainous 
country, owing especially to the miserable construction of the 
houses and their sites on the edges of crumbling precipices, or on 
steep declivities. 
The effects at the surface consisted in the opening of cracks, 
slipping of the surface material, especially the Tertiary and Qua- 
ternary, and in temporary and permanent changes of level up- 
ward and downward. 
The first shock was preceded and accompanied by low barome- 
tric pressure and followed by abundant rain, with lightning and 
other atmospheric electrical phenomena. 
The Andalusian seismic period, begun in 1884, and probably not 
yet ended, is referable to the same seismic heat-center which 
caused the disastrous earthquakes of Malaga in 1581 and 1680, 
for these were wholly similar to the recent earthquake in area 
and center of movement. 
5. Holocrystalline granitic structure in eruptive rocks of Ter- 
tiary age.—As is well known, the age-classification of massive 
rocks has, within the last few years, been largely invalidated by 
the discovery of several localities where Tertiary surface rocks of 
the ordinary type pass gradually into coarsely crystalline, grani- 
toid varieties as they are traced downward. The “ Nevadite ” of 
von Richthofen, although shown by Hague and Iddings to con- 
tain some glassy base, is essentially a granitoid dacite. The in- 
vestigations of Hague and Iddings at the Comstock lode; of 
Judd on the tertiary peridotites and gabbros of the western coast 
of Scotland; and of Lotti on similar rocks in northern Italy, con- 
¢lusively prove that the physical conditions under which a rock 
mass solidifies, and not the geological ¢éme of its solidification, 
determine its structure. Coarsely granular rocks are more abund- 
ant in earlier formations because their superficial equivalents have 
been removed by erosion, while in the younger deposits there has 
been no time for this and hence the coarser rocks are mostly still 
deeply buried. Only as expressing this fact, is the age-classifica- 
tion of massive rocks now to be considered as useful. 
A very important contribution has recently been made to this 
interesting subject by Professor Alfred Stelzner of Freiberg, in 
his newly published volume on the Geology of the Argentine 
Republic. (Beitrige zur Geologie und Paliontologie der Argen- 
tinischen Republik. 1. Geologischen Theil. . 4°. Cassel und Ber- 
lin, 1885, pp. 329, with a colored geological map and three 
sheets of profiles.) This work contains the results of the scientific 
expeditions made in the region of the Andes by the author dur- 
ing his residence as professor in the National University at 
Cordova, between the years 1871 and 1874. It is filled with val- 
uable observations relating to all the geological formations en- 
countered and contains detailed petrographical descriptions of 
. the massive rocks. It is, however, to the contents of chapters 
Xvill and xix (pp. 198-213) which relate to the Tertiary Eruptive 
Rocks with a granitic habit, that it is desired to call particular 
attention, 
