March 31, 1905.] 



SCIENCE. 



511 



The basin of Lake Minnewaska is vertical- 

 walled except at the southwestern end. The 

 cliffs are highest under Cliff House, where they 

 stand 160 feet above the surface of the lake and 

 65 feet below it. The grit' is probably about 230 

 feet thick here. The walls are pierced \>y four 

 crevasses now filled with drift — the remains 

 of two fissures crossing each other at the deep- 

 est point in the lake, 74 feet deep. There is 

 no drift in the lake basin, not even under the 

 south-facing cliffs, although the fissure run- 

 ning S. 25° W. is filled, and the transverse 

 breach is blocked to 150 feet above the lake. 

 The glaciation is here S. 10° W. The cause 

 of the absence of drift is not clear ; elsewhere 

 the cliffs are heavilj' skirted. 



Lake Awosting lies along a vertical fault 

 plane drift filled at both ends. The fault 

 has not been studied. The north wall of the 

 Palmaghat is a vertical fault of 200 feet 

 throw. Both these faults seem to be derived 

 from the overthrown anticline of the Coxing- 

 kill escarpment. Mr. Darton is in error in 

 declaring the absence of extended faults. 



The next paper was by Dr. A. A. Julien on 

 the ' Determination of Brucite as a Rock Con- 

 stituent.' 



After a brief review of the life of Dr. Archi- 

 bald Bruce, of New York City, the discoverer 

 of the mineral, the fact of its wide distribu- 

 tion was set forth, both in limestones and ser- 

 pentinoids, either in its unchanged condition 

 or in the form of its derivatives, especially 

 magnesite and hydromagnesite, as maintained 

 by Volger in 1855. The following are its 

 most marked characteristics for recognition 

 as a rock constituent. 



1. In addition to the known basal cleavage, 

 two other systems may be distinguished on 

 plates or folia; that of the hexagonal prism, 

 often becoming rhombohedral, intersecting at 

 60° or 120° ; and that of the hexagonal 

 pyramid, intersecting at 90°. 



2. Nemalitic structure or fibration, com- 

 monly occurring in brucite within serpenti- 

 noids subjected to dynamic stresses. The 

 major axis of elasticity always lies parallel 

 to the direction of the fibers. 



3. Refractive index 1.57, sufficient, when the 

 associated minerals are pure, to distinguish it 



by the Becke method from serpentine on the 

 one hand and from amphiboles, dolomite, etc., 

 on the other. 



4. Birefringence (7 — a = 0.020), present- 

 ing interference colors of the upper first order 

 up to sky blue of lower second order, in plates 

 or sections of the usual thinness. 



5. Characteristic strain phenomena ; partic- 

 ularly by disturbance of the interference 

 figure, examined by convergent light in basal 

 cleavage plates or folia ; also by a variable, 

 small extinction angle in sections parallel to 

 the vertical axis. 



6. Optically positive character of the uni- 

 axial figure, in distinction from talc, ser- 

 pentine, etc. 



7. Occasional twinning, observed in crystals 

 enclosed in limestone. 



8. Certain chemical tests, in confirmation 

 of the optical diagnosis. 



A. W. Grabau, 



Secretary. 



Columbia University. 



the torrey botanical club. 



The meeting was held at the New York 

 Botanical Garden, February 22, 1905, Pro- 

 fessor L. M. Underwood in the chair and 

 twenty-one members present. 



A contribution to the local flora by Mrs. 

 Livingston and Miss Crane was communi- 

 cated by W. A. Murrill and read by Professor 

 Underwood. The authors had worked on the 

 fungi, and had identified 195 species in 82 

 genera and 17 families, all from Scarsdale, 

 N. Y. The balance of the program consisted 

 of remarks on the genus Lycopodium, being 

 some of the results of the joint labors of Pro- 

 fessor F. E. Lloyd and Professor L. M. Under- 

 wood, which will soon be published in the 

 Bulletin, Professor Lloyd spoke from a mor- 

 phological standpoint and Professor Under- 

 wood from a more general one. 



Professor Lloyd called attention to the dif- 

 ferences which were found to be diagnostic, 

 that were brought out by the wet method used 

 for the investigations, differences not distin- 

 guishable in dried material. The lycopods fall 

 naturally into two physiological groups as 

 shown by their morphological characters, de- 



