Journal of Applied Microscopy. 579 



Iridium type of Fizeau apparatus, in wliicli tlie effective expansion is the 

 difference between the expansion of the crystal and that of the screws of the 

 tripod ; an extra piece made of aluminum, the expansion of which is two and one 

 half times that of the Pt Ir alloy for the same temperature change. 



The proper thickness of aluminum to counteract the expansion of the known 

 length of Pt Ir screw, is introduced, usually in the form of a cylinder resting on 

 top of the crystal plate. The upper surface of the aluminum cylinder is polished. 

 On heating, the screws expand, raising the glass wedge which rests upon them, the 

 crystal and aluminum cylinder also expand in the same direction, and the effect- 

 ive change in the thickness of the film between glass and aluminum is due only 

 to the expansion of the crystal. 



An elaborate forty-page description of apparatus and its use is given. 



A. J. M. 



NEWS AND NOTES. 



One Method of Teaching Physiological Botany. — A little experiment 

 was made during the spring term of 1899. It so happened that the Junior and 

 Sophomore classes were to take botany together. Each class had had botany 

 in the spring term of the Freshman year under the same instructor, using the 

 same text-book, with the exception of one young lady in the Freshman class who 

 had never studied the subject. MacDougal's " Plant Physiology" was used as a 

 text-book and supplemented by twelve others as the case required. Lectures 

 were occasionally given by the instructor which consumed only a part of the 

 daily period. The rest of the periods of 55 minutes each were consumed in 

 hearing, discussing, and taking notes on reports made by the members of the 

 class on literature that had been previously assigned to each member. Nine 

 periodicals devoted entirely or in part to botany and elementary texts on botany 

 was the literature on which reports were required. There was one period of two 

 hours per week devoted to making experiments, usually such as the student 

 might select either from the leading text or some of the supplementary texts. In 

 this way the students were interested from the beginning to the end of the term. 

 Interest on the part of the student is perhaps the prime essential for successful 

 teaching. Nearly all of the class, particularly the young men, seemed delighted 

 to have an opportunity to report fully (and as freely as time would permit) what 

 they had found in the literature assigned. The instructor would sometimes take 

 a seat in the class and let the student have the floor completely for the time 

 being. He would instruct without assuming that the students knew a good deal 

 that they did not, which some instructors are quite liable to do. 



When the end of the term came all of the class passed except two young 

 women. 



One of the interesting results was that among the young women, the one who 

 had never before studied the subject passed highest. 



This kind of work could not probably be so well done by the ordinary stu- 

 dents of a Freshman class, nor could the scheme be so thoroughly carried out in 

 large sections of classes. 



