M. TECHNOLOGY. 593 



openings at the base. The progress of the heating may be 

 noticed by holding a small mirror beneath. With a furnace 

 arranged in this manner persons have succeeded in melting 

 six hundred grains of cast iron in a small porcelain crucible 

 in less than a quarter of an hour. 21 A, M^ci^, 1873, 471. 



MIRRORS FOR REFLECTING TELESCOPES. 



Professor H. L. Smith, of Hobart College, Geneva, N. Y., 

 makes the following communication regarding an improve- 

 ment in the manner of making very large mirrors for reflect- 

 ing telescopes. He says : " I ground and prepared a bell- 

 metal speculum, which I coated with nickel, and this, when 

 polished, proved to be more reflective (at least I thought so) 

 tlian speculum metal. The two objects which I sought were 

 first, to have a polished surface unattackable by sulphuret- 

 ed hydrogen (this, for example, is not injured by packing 

 with lucifer matches), and, secondly, for large specula, doing 

 most of the work by the turning -tool and lathe. I really 

 think a large (say three-feet) mirror, coated w-ith nickel, but 

 cast of iron, and finished mostly in the lathe, while it would 

 not cost the tenth of a similar-sized speculum metal, would 

 be almost equal to silvered glass of the same size, and vastly 

 more enduring as to polish." 12 A^ Ajyril 17, 1873, 475. 



ARTIFICIAL GRASS FR0:M PARCHMENT PAPER. 



A Step tow^ard the fabrication of artificial flowers from 

 parchment paper has been made in the successful manufact- 

 ure of artificial grass, which has the advantage of being 

 much tougher than that from common and oiled paper, and 

 in no way inferior to it. 



VEGETABLE PARCHMENT. 



The employment of vegetable parchment seems capable of 

 great expansion by adaptation of its character and price to 

 diflerent purposes ; and it may be expected that increased 

 consumption will cheapen its production and lead to still fur- 

 ther uses. In many cases it already rejolaces waxed cloth, 

 mole-skin, etc. As a water-proof w raj^ping it is serviceable 

 in the form of envelopes for valuable papers, and for inclosing 

 small samples, especially of moist colors and dye-stufis. It 

 may also prove desirable for artificial flowers, if suitably 



