Januaky 29, 1904.] 



SCIENCE. 



165 



tem of conies corresponding to it in the 

 manner above explained, the secondary 

 system. It is shown that the equation of 

 a conic of the secondary system is of the 

 fourth degree with respect to the param- 

 eter and that, therefore, four conies of 

 the secondary system iDass through any 

 particular point in the plane. 



The equation of the radical axis of two 

 circles, ij- and ij-' , of the system is 



F , H 



F and H being of the fourth degree in a* 

 and IJ- and G of the third degree. It thus 

 appears that there are sixteen sets of 

 values of /-/. and ij.' for which this equation 

 represents the same radical axis; that is, 

 there are sixteen pairs of circles having the 

 same radical axis. Moreover, to these 

 thirty-two circles there correspond thirty- 

 two conies of the secondary system, all of 

 which are tangent to the same radical axis. 

 The paper includes, by way of introduc- 

 tion, a brief discussion of the equation 



A Neiv Type of Transit-Room Shutter: 

 Professor David Todd, Amherst, Massa- 

 chusetts. 



The type of shutter here described is 

 that used to cover the two transit slits of 

 the new observatory of Amherst College. 

 These slits have a clear opening of 100° 

 each way from the zenith and are three 

 and one half feet in width. Each shutter 

 is twenty-one feet long and sixteen feet 

 high. It is made of structural steel with 

 two vertical members and one truss mem- 

 ber across the roof. Its weight is about 

 three thousand pounds. 



The entire shutter moves as a unit upon, 

 ball-bearing rollers underneath the verti- 

 cal members. These rollers travel upon 

 rails lying east and west along the north 

 and south walls of the building. The two 



ends of the shutter are made to travel in 

 unison by means of rack and pinions with 

 sprocket wheels and link-belt chain. 



The roof-member travels ten inches 

 above the roof of the transit room, thus 

 clearing all ordinary depths of snow. 

 Only the bottom of this member is covered 

 in, the structural elements of its top and 

 sides being left exposed as in bridge work. 

 Wind thrust is thereby minimized. 



The entire shutter opens or closes full 

 width in 'four seconds, by eight turns of 

 a haud wheel. A small shaft lock holds it 

 firmly in either position. 



Laenas Gifford Weld, 



Secretary. 



SECTION 0, BOTANY. 

 Section G at the St. Louis meeting was 

 organized, under the chairmanship of Pro- 

 fessor T. H. Maebride, on December 28, 

 1903. The other officers were as follows: 



Secretary — F. E. Lloyd. 



Councillor — Wm. Trelease. 



Sectional Committee — T. H. Maebride, vice- 

 president, 1904; F. E. Lloyd, secretary, 1904-1908; 

 F. V. Coville, vice-president, 1903; C. J. Chamber- 

 lain, secretary, 1903; W. A. Kellerman (one year), 

 F. S. Earle (two years), C. E. Bessey (three 

 years), W. T. Beal (four years), F. E. Clements 

 (five years) . 



Member to General Committee — C. L. Shear. 



Meetings of the section for the reading 

 of papers and for other business were held 

 on December 28, 29, 30, 31 and January 

 1. The Mycological Society and the Bota- 

 nists of the Central States met conjointly 

 with the section. 



A committee consisting of Professor C. 

 E. Bessey, Dr. B. T. Galloway and Pro- 

 fessor C. MacMillan drew up a resolution 

 strongly endorsing the efforts at present 

 being made looking toward the passage 

 of such laws by Congress as will provide 

 for the perpetual preservation of the Cala- 

 veras Grove of Big Trees in California. 



On Friday morning the section, together 



