24 



ANNUAL REPORT OF THE 



The students of Geology 22a carried on experimental work on 

 two subjects. Mr. C. W. Dorsey made a series of models of 

 glacial sand plains by means of an apparatus imitating the con- 

 ditions of glacial drainage, and the resulting delta deposits were 

 studied minutely with respect to form, bedding in cross-section, 

 influence of water level, and other variable conditions. Messrs. W. 

 A. Baldwin and E. E. McCarthy, the other students of the course, 

 were led through a series of experiments imitative of the deforma- 

 tion of stratified rocks under compression, following in general the 

 plan adopted by Mr. Bailey Willis in his work on the " Mechanics 

 of Appalachian Structure" (13th Ann. Rep. U. S. Geol. Survey). 

 For general work of this sort a massive compression chest was 

 constructed of oak, provided with two heavy thrust pistons at 

 opposite ends, which can be advanced by screws. The models are 

 cast from mixtures of wax and plaster, and are then submitted to 

 slow compression under a heavy load of fine shot. The apparatus 

 is so made that the amount of movement and pressure is registered 

 on special indices at various points ; a metronome is used for 

 regulating the rate of compression. Each model is removed and 

 photographed at different stages of deformation, and the records 

 so obtained are used by the students for comparative study with 

 structures in the field and with published descriptions of similar 

 phenomena. 



In addition to the apparatus above described, and in preparation 

 for a special course in Experimental and Dynamical Geology, to be 

 given in 1896-97, the following instruments have been collected : — 



Machine for the reproduction and measurement of Ripple-mark. 



Ring-shaped tank for producing a continuous current of water ; 

 for the study of Ripple-drift, rate of transportation of material in 

 suspension, etc. 



Five vessels of different form, for the study and optical projec- 

 tion of vortical movements in a liquid, as affecting conditions of 

 transportation and deposition. 



Gas Furnace, model Leclerc and Forquignon, made by Lequeux 

 in Paris, with adjustable blowpipe and improved hydraulic blast 

 (after Damoiseau). The latter may also be used as sucking or 

 vacuum pump. This apparatus is most useful for general work in 

 the synthesis of minerals and rocks. 



Electric Furnace, model O'Neill, for experiments requiring 

 excessively high temperature. 



