750 



SCIENCE. 



[N. S. Vol. XI. No. 280. 



Sap moves freely both up and down toward the 

 tap-hole with the grain of the wood, but very 

 little or not at all across the grain. 



Other problems mentioned are still under in- 

 vestigation. F. A. Lucas. 



NEW YOEK ACADEMY OF SCIENCES. 

 SECTION OF GEOLOGY AND MINERALOGY. 



The meeting on April 16, 1900, was held at 

 12 West 31st Street, Dr. A. A. Julien presiding 

 and 29 persons present. 



Professor Stevenson, in behalf of the com- 

 mittee appointed to prepare a minute respect- 

 ing the late Professor Hubbard, presented an 

 obituary notice which is published on page 742 

 above. 



Dr. R. Ellsworth Call presented ' Some Pre- 

 liminary Notes on Crystal Growths in Mam- 

 mioth Cave.' He first gave a brief resume of 

 the geology of the vicinity of Mammoth Cave. 

 The strata making the geologic section are 

 nearly horizontal and all the rocks forming the 

 cavern are of sub-carboniferous age. The re- 

 gion of the cavern is capped with sandstones 

 of the Chester Group 500 feet thick, beneath 

 which are oolitic and other limestones, in which 

 the cavern is excavated to a thickness of over 

 350 feet. The drainage level of the cavern is 

 determined by the present level of Green River. 

 Five different levels have existed during geo- 

 logic time. No gypsiferous strata are known in 

 the region. The overlying sandstone is usually 

 quite ferruginous ; but no pyrite occurs in 

 either strata. Secondary crystallization has 

 occurred in many of the stalactites causing 

 them to simulate the fibrous appearance some- 

 times assumed by aragonite. The stalactites of 

 recent origin almost all have a downward-pro- 

 jecting tree root as their origin of fixation, or 

 are beneath sink-holes. The chief objects of 

 miueralogical interest are the gypsum crystals 

 which cover the sides and ceilings of certain 

 avenues in the cavern, in the upper of the five 

 levels only, and not in any levels now occupied 

 by streams. These crystals are sometimes 

 curiously and remarkably contorted and the 

 terminations of the crystal masses are often 

 recurved in a direction contrary to the direc- 

 tion of gravitation. Occasionally the gj'psum 

 assumes a botryoidal form, but is commonly 



found as needles or aggregated in loose masses 

 of fibrous crystals. The gypsum crystals occur 

 only along cracks, and are built up by increase 

 from the base, while the calcium-carbonate 

 stalactites are always built up by additions to 

 their surface or terminations. It is difficult to 

 account for the large amount of sulphur needed 

 by assuming its origin in organic bodies, such 

 as plants and the forests which are now of 

 abundant growth in the region and have been 

 so for geologic ages. The origin of the carbon 

 dioxide necessary for the great work of solu- 

 tion which has been accomplished is likewise 

 found in the decaying vegetation. The origin 

 of the sulphuric acid required to produce these 

 enormous quantities of gypsum crj'stals, which 

 have fallen so abundantly as to fill up certain 

 avenues, is still problematic. Only one other 

 mineral is found, flocculent crystals of magne- 

 sium sulphate, pendant from the ceiling of two 

 or three small rooms. There are no calcite or 

 quartz crystals. The paper was illustrated by 

 lantern slides showing the peculiarities of the 

 stalactite and gypsum formations. 



Professor Kemp, in discussion, suggested that 

 the small percentage of sulphur present in the 

 limestones themselves might, after solution of 

 the latter, aggregate sufficient sulphur to afford 

 gypsum along the crevices. Doctor Julien and 

 Professor Stevenson each cited cases in 'the 

 Caribbean and Bermuda Islands where the 

 amount of vegetation now or formerly growing 

 on the surface was insufficient to accomplish 

 the solution required for the great caves which 

 exist in the coral limestones, both of tertiary 

 and recent growth in the islands. 



A paper by Doctor E. O. Hovey, on the 

 ' Scenery of the Harney Park District in the 

 Black Hills, South Dakota ' (illustrated with 

 lantern slides), was read by Professor Kemp, 

 owing to the former's unavoidable absence. 

 After a brief resume of the geology of the Black 

 Hills district, a series of views was shown illus- 

 trative of the extraordinary erosion forms of 

 the schists and pegmatites of the Harney Peak 

 district. The photographs also showed the tin 

 mines of the Black Hills, in which spodumene 

 crystals of large size have recently been ob- 

 tained as a valuable source of Lithium, as a 

 commercial product. One spodumene crystal 



