286 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
its great abundance was unsuspected before they began their long 
series of excellent analyses, though its wide distribution had been 
noted. 
It is also noteworthy that, with the exception of iron, aluminum, 
manganese, and nickel, none of the metals commonly used as such 
appear in the list, while others, which are of very limited practical 
application, are present. While nearly, if not quite, all of the ele- 
ments are presumably present in igneous rocks, the average amounts 
of those not given in the list are so extremely small that they may 
be regarded as minor corrections to be applied in the future to cer- 
tain of those here given, since nearly all of them would be precipi- 
tated and weighed in the course of analysis with some of those more 
abundant. . 
In the important paper cited above, Vogt has discussed the probable 
amounts of these missing elements, and a brief statement of those of 
his results which pertain to the more important metallurgical elements 
‘may be given. The estimates, it must be premised, are but approxi- 
mations, and only indicate the magnitude of the several amounts as 
percentages of the earth’s crust. But they serve to show the average 
extremely small quantities of many metals and other elements which 
are usually regarded as quite common or at least not very rare. 
The percentage amounts of tin, zinc, and lead are expressed by a 
digit in the third or fourth decimal place, that of copper in the fourth 
or fifth, that of silver in the sixth or seventh, that of gold in the 
seventh or eighth, the amount of platinum being about the same. 
Mercury is rather more abundant than silver, and arsenic, antimony, 
molybdenum, and tungsten less than copper and greater than silver ; 
while bismuth, selenium, and tellurium are less abundant than silver 
but more so than gold. 
III. PETROGRAPHIC PROVINCES. 
More than thirty years ago Vogelsang * pointed out that the igneous 
rocks of certain districts—called by him geognostische Bezirke— 
showed certain textural or mineral characters in common, which 
served to distinguish them from the rocks of other districts. The 
same idea was expressed later by Judd,’ who introduced the term 
petrographic province, and was afterwards elaborated by Iddings,’ 
who lkened the districts of similar rocks to families and referred to 
their relationships as “ Consanguinity.” Neither Judd nor Iddings 
“@H. Vogelsang, Zeitschrift der deutschen geologischen Gessellschaft, vol. 24, 
No. 3, p. 525 (May-July, 1872). 
oJ. W. Judd, Quarterly Journal of Geological Society, vol. 42, pt. 1, No. 165, 
p. 54 (Keb. 1, 1886). 
¢ J. P. Iddings, Bulletin of the Philosophical Society of Washington, vol. 12, 
pp. 128-144 (1892), 
