TO CORRESPONDENTS. 



L. A. C. — The word cirri in the Meteorological Table, denotes that 

 kind of cloud as visible at ihe time of the observation. Meteorolo- 

 gists recognise three principal forms of clouds, and their combina- 

 tions. The light thin clouds, high up in the air, in long streks or 

 curls are denominated, cimis clouds. Those that are piled up 

 like heaps of wool are termed cumulus. Flat level lying clouds, 

 stratus. A combination of any two, takes the name of both kinds, 

 as cirro stratus, cirro cumulus, etc. The rain clouds is named 

 I^imhus. 



J. M. — You can obtain good achromatic microscopes at a moder- 

 ate price, of Jas. Foster, Optican, S. W. corner of 5th and Race 

 Sts., Cin. — QuEKETTS, treatise on the Microscope can be purchased 

 of Robert Clarke, Bookseller, opposite the U. S. Hotel on 6th, 

 St. He has also Carpenter's and Hogg's work on the same 

 subject. 



Melted Stone. — Near Birmingham, England, works have recently 

 been started for the manufacture of architectural decorations in 

 basalt by melting and casting in hot moulds. The products are very 

 firm and beautiful, and are assumed to be very durable. When cast 

 in cold moulds, a glossy lava termed obsidian is produced. The 

 material generally employed is the ragstone of the neighborhood, 

 but furnaces have been erected for the reduction of quartz by di- 

 rect fusion according to a new process, in which the pulverized 

 quartz is mixed with flour spar, lime, and oxyde of iron, which 

 agents combine with the silica and render the whole perfectly fluid. 



Erata.— On page 267 of the June number, under the heading of 

 " WooPBURN Farm," instead of 280 acres read 2800 acres. 

 336 



