22 



V. REPORT ON THE PETROGRAPHICAL LABORATORY. 



By J. Eliot AVolff. 



Two courses were given in Petrography, an elementary course 

 in General Petrography, and an advanced course in Petrographi- 

 cal Research. The first course was attended by fourteen stu- 

 dents, and the second by five, — in all, the largest number since 

 the establishment of the Laboratory. 



The equipment was materially enlarged by the purchase of a 

 large Voigt and Hochgesang petrographical microscope and two 

 medium-sized microscopes, and in other ways. The collections 

 were increased by the purchase of 150 rock specimens from 

 Krantz in Bonn, and otherwise, and by the addition of 350 thin 

 sections of rocks. The laboratory is also enabled to use, by the 

 kindness of Mr. Agassiz, the large microphotographic and pro- 

 jecting apparatus of Zeiss, recently purchased. 



It is a pleasure to record the gift to the University for the use 

 of the Geological Department, by Dr. Lucius G. Hubbard, of the 

 large and valuable collection of rocks from the Laacher See re- 

 gion in German} r , which formed the basis of his monograph in 

 Tschermak's Miner alogische und Petrographische Mittheilungen, 

 1887, 64 Beitrage zur Kentniss der Noseanfiihrenden Auswurflinge 

 des Laacher Sees." 



Petrographical investigation was begun on the felsites of the 

 Boston region by several students in common, which it is hoped 

 will continue this year. 



A monograph was completed by Mr. G. L. Collie on Conanicnt 

 Island, R. I., and investigations were carried on by Mr. J. B. 

 Wood w orth on rocks of the Narragansett Basin, and by Mr. 

 L. G. Westgate on rocks from Jenny Jump Mountain, N. J. A 

 paper, by the instructor jointly with R. S. Tarr, u On Akmite 

 Trachytes from the Craz}- Mountains," is ready for publication. 



The instructor was engaged during the year with several as- 

 sistants in the stud} r of the structure of the Archsean Highlands 

 of New Jersey, and the study of the eruptive rocks of the Crazy 

 Mountains was continued. 



