Procctdinf^s of Scientific Societies. 205 



Dr. (iray read ri pajK-r oti tlic anatomy of the insect trachea, 

 largely made up of" references to tlie early literature of tlie sid^ject. 



July 1, 1S91, C. W. \Vo(id\vorth. of the A»;ricultural Ex])eriment 

 Station at Herkelcv, was present and exhibited some slides, showings 

 the scale insect infesting; the leaves of the olive. He called attention 

 to the fact that tx'rtain closely allied s]X'cies of scale insect were 

 invested with an outer coverinj; jjroduced by exuvia, or bv harden- 

 ing of the skin, while in the si)ecies under consideration this outer 

 covering seemed almost entirely composed of tlie stellate hairs 

 accumulated from the under side of the leaf of the olive on which it 

 feeds. .\s the larva grows it insinuates itself beneath these stellate 

 hairs, which become broken from the leaf and attached to the skin 

 of the (levelo]jing insect. Mr. Woodworth exhibited two slides last 

 evening, one the young larval skin, of about one-fourth tlie adult 

 size, and the other the com])lete adult form. 



Henry G. Hanks was present and exhibited sonic curious so- 

 called lava, recently obtained from Butte county. In November 

 last Mr. Hanks read a paper before this society on 'Certain Mag- 

 netic Rocks,' in which he assumed that the rocks at Tucson were 

 nearly identical with the Table Mountain ca])]3ing, which overlies 

 the deej) good placers of this State, jirotecting them from denuda- 

 tion and dispersion. During a recent visit to Butte county for the 

 stud\' of this formation he made two im]:)ortant discoveries bearing 

 on this subject, which at least afford strong evidence in favor of the 

 opinion stated in the pa])er referred to, that the rocks were not of 

 igneous, but of a(pieous origin. 



The first discovery was at the mouth of Chico canyon, where 

 William FVoud showed him some cylindrical natural tubes in the 

 so-called lava, which Mr. Hanks believes to be solfatarie 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 believed may be found elsewhere. The infer- 

 ence drawn from this discovery is that these rocks, supposed to be 

 igneous, are really overflows of solfatarie mud ; otherwise it would 

 be impossible to account for the steam ])i]3es, for the rock must have 

 been at one time soft .and permeable. 



The second discovery was a fragment of the same rock obtained 

 from Mrs. Caroline H. Church of the .\urora drift mine, near Maga- 

 lia, in which there is a cast of a pine cone, so perfect that when 

 li(|uid ])laster of paris is ])oured in a model of a cone is obtained 

 showing every detail of structure. Mr Hanks has examined the 

 cast closely with the microscope, and could find no trace of charcoal. 

 Nor can it be possible that the rock was hot, for had the cone 



