■348 



SCIENCE 



[N. S. Vol. XXVII. No. 687 



.nary sands and clays. Clays and sands, how- 

 ever, have a density of about 2.5, while that of 

 ■salt is 2.16, and the expansive force of the salt 

 from the crystallizing source will be very cir- 

 cumscribed and the salt domes local in char- 

 acter. The domes in both Texas and Alabama 

 are of similar origin, though some may consist 

 in large part of gypsum, limestone or sul- 

 phur as well as of salt. Some of these cores 

 of salts have been pushed up through Cre- 

 taceous strata, others through Eocene and 

 many into the Quaternary; they are distinctly 

 exogenoiis in character and may be termed 

 foreign intrusions. Similar occurrences of 

 salt domes have been noted at Ischel in 

 Algeria and seemingly in the Salt Eange of 

 India. The material for these salt domes is 

 considered to have been taken up by the cir- 

 culating solutions from the late Paleozoic or 

 Mesozoic salt and gypsum layers which con- 

 stitute the floor of the pitching trough of the 

 Mississippi embayment. The arching or dom- 

 ing up of pervious and impervious strata 

 by the crystallizing salt domes facilitates the 

 segregation of the oil and gas which are also 

 found in this region. 



Regular Program 

 The Occurrence of the Silurian in, Western 



America: Mr. E. M. Kindle. 



Mr. Kindle reviewed briefly the evidence on 

 which many geologists have questioned the 

 reported occurrences of Silurian strata in the 

 western states. Three localities which had 

 come under the speaker's observation were 

 cited from which distinctly characteristic 

 Silurian faunas had been obtained. These 

 localities are in the Wasatch Mountains of 

 Utah, ' in southeastern Alaska and in north- 

 eastern Alaska. The bearing of these observa- 

 tions on one of the problems of Silurian 

 paleogeography was pointed out. 



The Origin of Limestone Breccias: Mr. 



Marius R. Campbell. 



There is such a common tendency to ascribe 

 all brecciation of rocks to movement, that the 

 writer takes this opportunity to describe the 

 formation of a solution breccia which, 

 fortunately, he was able to observe in various 



stages of its development near Fort Stanton, 

 New Mexico. The exposure is in a narrow 

 box canyon cut in horizontally bedded carbon- 

 iferous limestone. 



The initial stage of the process consisted of 

 a solution channel formed by a stream of run- 

 ning water. From this channel the limestone 

 has been dissolved along the bedding planes 

 for varying distances, amounting, in some 

 cases, to as much as fifty feet. As the lime- 

 stone is variable in composition, the cavities 

 are irregular, extending in many places 

 vertically through the beds, probably along in- 

 cipient joint cracks. In some places this ac- 

 tion had gone on until the more siliceous por- 

 tions of the rock remained as a mere honey- 

 comb, filling a cavity possibly 100 feet long 

 and 8 or 10 feet high. Subsequently the rock 

 had been eaten through and droppings had 

 filled the cavern with an irregular mass of 

 subangular fragments. The final stage showed 

 this mass recemented by the calcareous waters 

 into a solid breccia completely filling the 

 cavern in which it was formed. 



Several examples were seen where this 

 process had gone on to its culmination, and in 

 such cases one could follow the bedding of the 

 limestone above and below and on both sides 

 of the original cavern, but within all trace of 

 bedding had been obliterated. If this process 

 were repeated many, many times, it is con- 

 ceivable that it might result in the complete 

 brecciation of certain beds which were more 

 soluble than the rocks above and below and 

 thus give rise to such a formation as the 

 " sheet ground " of the Joplin zinc and lead 

 district. 



A Recent Vein at Ojo Caliente, New Mexico: 



W. LiNDGREN. 



Ojo Caliente is a small village situated in 

 northern New Mexico, about fifteen miles west 

 of Barranca station on the Denver and Eio 

 Grande road. Strong mineral springs of great 

 local reputation issue here from the bottom 

 lands of a small tributary to the Chama 

 River. The water has been analyzed by Dr. 

 Hillebrand. It is of a strongly alkaline char- 

 acter and contains much sodium carbonate. 

 Other interesting constituents are boron. 



