RECORDS OF MEETINGS OF 1907 339 



It was found that at the end of May the six-pointed type of leaf constitutes 

 over half the total foliage (.58 in 1905; .65 in 1906), and that the four- 

 pointed type is totally absent. During the next month there is a remark- 

 able growth of four-pointed leaves, so that at the end of June they constitute 

 over 50 per cent, of the total foliage. The six-pointed leaves become re- 

 duced to about 35 per cent, of the total. During the remainder of the 

 summer these figures vacillate only within about 5 per cent. The leaves 

 with 8, 10, 12 and 14 points were also studied; each makes up only a small 

 per cent, of the total foliage, the last being very rare. 



The talk was illustrated by charts and specimens. 



The Section then adjourned. 



M. A. BiGELOW, 



Secretary. 



SECTION OF ASTRONOMY, PHYSICS AND CHEMISTRY. 



May 20, 1907. 



Section met at 8:15 P. M., Vice-President Trowbridge presiding. 



The minutes of the last meeting of the Section were read and approved. 



The following program was then offered: 



F. W. Pedersen, Viscosity of the Vapors of Certain Isometric 



Ethers. 

 William Campbell, On the Iron-Carbon Series of Alloys. 



Summary of Papers. 



Dr. Pedersen, in his paper, dealt with the influence of molecular structure 

 upon the internal friction of the vapors of certain isometric ethers. The 

 viscosity coefficients of various ether vapors at 100° c. were obtained by the 

 well-known transpiration method. The molecules of a Tertiary compound 

 were shown to be smaller than those of a secondary, which in turn are 

 smaller than those of a primary. 



Professor Campbell revised the various published equilibrium curves 

 of the carbon-iron series, and by a series of lantern slides showed the various 

 changes of structure which take place (a) by variation in carbon, (b) by heat 

 annealing. It was demonstrated that two systems occur (1) Austenite 

 (mixed crystals) : cementite, (2) Austenite (mixed crystals) : graphite. The 

 former is unstable; the latter stable. 



