ABSTRACTS OF PAPERS 27 



bent laminse there is evidence of a space filled in, the filling showing lamina?. 

 Laminas bent about a concretion hereby seem to prove syngenetic origin. 



Prof. A. 0. Lawson : It is probable that in cases vphere cone-in-cone struc- 

 ture is confined to a particular bed of wide extent the structure is due to the 

 escape of gas from decaying organic matter beneath the layer in question be- 

 fore its consolidation, when it was in a more or less viscous or pasty condition. 



Dr. H. S. Washington : In connection with the formation of cone-in-cone 

 structure, attention may be called to the occurrence of concentric thinning 

 spherical shells (saucers) beneath bombs that had fallen in the tuffs of one 

 of the volcanoes. Their origin may be assigned, somewhat doubtfully, to the 

 pressure produced by the impact of the bomb. 



Prof. W. A. Taer : Cone-in-cone occurs on the upper and more rarely on the 

 lower side of the concretions which occur in the Mawry member of the Graneros 

 shale. In view of the horizontal stratification lines in these concretions which 

 are discontinuous with those around the concretions, it seems doubtful that 

 .the cone-in-cone was developed by pressure. Recent studies by the writer, as 

 well as published views, I'aise the question of origin of the cone-in-cone. The 

 old view, that they were due to pressure, may be questioned and the origin of 

 cone-in-cone by crystallization be the actual case. In this particular case cer- 

 tainly the concretion was syngenetic and therefore the cone-in-cone not due to 

 pressure. 



Eead from manuscript. 



The paper was discussed by Messrs. Stephen Taber, G. H. Chadwick;, 

 W. H. Twenhofel, Sidney Powers, R. D, Salisbury, A. C Lawson, W, H. 

 Bucher, and H. S. Washington. 



RAIN-DROP IMPRESSIONS AND MARES OP SOMEWHAT SIMILAR APPEARANCE 



BY W. H. TWENHOFEL 



Read from manuscript. 



Discussion 



Dr. H. S. Washington remarked on the globules of volcanic dust produced 

 by rain descending through the eruption cloud of the 1790 explosive outbreak 

 of Kilauea, Hawaii, and preserved in the ash. 



Dr. E. O. HovEY cited the similar abundant globules formed during the ex- 

 plosive eruption of Mount Pele, Martinique, in 1902. 



STRUCTURAL FEATURES OP INDIANA 

 BY STEPHEN VISHEE ^ 



(Abstract) 



The outstanding structural features of Indiana may be enumerated under 

 the following heads : 



* Introduced by Ellsworth Huntington. 



