188 THE AMERICAN MONTHLY [August, 



MICROSCOPICAL SOCIETIES. 



San Francisco, Cal. — Wm. E. Loy, Sedy. 



June 7, i8gi. — President Wickson in the chair. Despite the fact 

 that many members were out of the city on vacation or business, a very 

 good attendance was noted, and the proceedings proved of more than 

 ordinary interest. Four new resident members were elected, viz : 

 H. 0."Perley, M. D. ; B. Noyes, George O. Mitchell, and E. F. 

 Glasher. 



The President spoke of the efficient work performed by the Commit- 

 tee having in charge the removal of the Society's effects, and the 

 arrangements for the anniversary meeting, so successfully held last 

 month. A vote of thanks was unanimously tendered that Committee, 

 and special mention was made of the services rendered by Mrs. Breck- 

 enfeld and Mrs. Loy in furnishing and decorating the rooms for the 

 occasion. 



C. VV. Woodworth, of the Agricultural Experiment Station at Berke- 

 ley, was present and exhibited some slides, showing the scale insect in- 

 festing the leaves of the olive. He called attention to the fact that 

 certain closely allied species of scale insects were invested with an outer 

 covering produced by exuvia, or by hardening of the skin, while in the 

 species under consideration this outer covering seemed almost entirely 

 composed of the stellate haii^s accumulated from the under side of the 

 leaf of the olive on which it feeds. As the lava grows it insinuates it- 

 self beneath these stellate hairs, which become broken from the leaf and 

 attached to the skin of the developing insect. Mr. Woodworth ex- 

 hibited two slides, one the young larval skin, of about one-fourth the 

 adult size, and the other the complete adult form. 



Henry G. Hanks exhibited some curious so-called lava, recently ob- 

 tained from Butte county. In November last Mr. Hanks read a paper 

 before this Society on " Certain Magnetic Rocks," in which he assumed 

 that the rooks at Tuscon were nearly identical with the Table Moun- 

 tain capping, which overlies the deep gold placers of this State, pro- 

 tecting them from denudation and dispersion. During a recent visit to 

 Butte county for the study of this formation, he made two important 

 discoveries bearing on this subject, which at least afford strong evidence 

 in favor of the opinion stated in the paper referred to, that the rocks 

 were not of igneous, but of aqueous, origin. 



The first discovery was at the mouth of Chico Canon, where William 

 Proud showed him some cylindrical natural tubes in the so-called lava, 

 which Mr. Hanks believes to be solfataric steam-pipes. These varied 

 from the size of a quill to three inches or more, and some of them are 

 at least four feet deep. They are not rare, but common, and, it is be- 

 lieved, may be found elsewhere. The inference drawn from this dis- 

 covery is that these rocks, supposed to be igneous, are really overflows 

 of solfataric mud ; otherwise it would be impossible to account for the 

 steam-pipes, for the rock must have been at one time soft and perme- 

 able. 



The second discovery was a fragment of the same rock obtained from 

 Mrs. Caroline H. Church of the Aui'ora drift mine, near Magalia, in 

 which there is the cast of a pine cone, so perfect that when liquid plas- 

 ter of paris is poured in a model of the cone is obtained, showing every 



