Review of Recent Geoloriicnl Liferatare. 135 
temporary state of volcanic activity during the Newark system. In 
contact with the fragmental strata the traps have in some places caused 
a generation of ejlidote and tourmaline and a general hardening: and 
sometimes a nodular and spotted aspect, as if crystallization had begun 
to act at innumerable points. 
This report is to be followed by a final memoir when the whole field 
has been studied. n. h. w. 
Observations on Popocatepetl and I.rtaccihuatl, icith a review of 
the geographic and geologic features of the vumntainH. Oliver G. 
Farbington. (Field Columbian Museum. Geol. Series, vo'. i, no. 2, 
1897.) Mr. Farrington has succeeded in adding much to our knowl- 
edge of these mountains, as well as condensing most of what was before 
known from earlier explorers. The description is accompanied by sev- 
eral photographic plates of the crater of Popocatepetl and of the glacier 
named Porfirio Dias by Heilprin, of which latter he gives the first ade- 
quate description. He found that this glacier, like many others of 
North America, is in a state of retreat. Popocatepetl is an extinct vol- 
cano, but Prof. Farrington is inclined to believe that Ixtaccihuatl gave 
forth only fissure flows of lava. This opinion is based on the homogen- 
eous and compact nature of the igneous rock of which the mountain is 
so largely composed, and the elongated form and direction of the valley 
in which the glacier lies, and on the absence of any known centre of 
volcanic activity. Of the two it is the older mountain, and is supposed 
to be about a thousand feet less high than Poijoeatepetl. The rock in 
both is essentially andesyte but with variations of texture. However, 
according to the Mexican geologists Aguilera and Ordonez the earliest 
eruptions of Popocatepetl were basic basalts, with olivine, the order of 
the variation in mineralogical composition being different from that 
found by Iddings in Electric peak. n. h. w. 
The f idler's earth of South Dakota. Heinrich Reis. (Trans. Am. 
Inst. Miu. Eng., July, 1897.) This clarifying and decolorizing agent 
has not been known in this countiy until within the past two years, 
when it was announced from Florida by the United States Geological 
Survey. Mr, Reis describes it from Fairburn, Custer county, and from 
Argyle and Minnekahta, South Dakota, giving several analyses. The 
deposits are large and are likely to take the place in this country en- 
tirely of that imported hitherto from England. n. h. w. 
Ticetitji-first annual report of the department of geologi/ and natu- 
ral resources, Indiana, W. S. Blatchi^ey, state geologist, Indianapo- 
lis, 1897. Mr. Blatchley has chapters as follows: The natural resources 
of Indiana: The petroleum industry in Indiana; Indiana caves and 
their fauna; A catalogue of the uncultivated ferns and fern allies and 
the flowering plants of Vigo county. Indiana. Other contributors to 
this report are: W. A. Noyes, Composition of Indiana coals: Hans Da- 
den, Some notes on the Black slate or Genessee shale of New Albany, 
Ind.: August F. Foerste, Report on the geology of the middle and up- 
per Silurian rocks of Clark, Jefferson, Ripley, Jennings and southern 
