TTire Qoth prepared for Lanthorns and other U/es. 41 j 



When this prepared wire cloth is fixed in the lanthorn, it muft be defended from moifture 

 by a coating of pure drying linfeed oil ; but even in this ftate it is not fit to be cx- 

 pofed to the weather. The eafc with which thefe lanthorns are repaired in cafe of acci- 

 ■dent, by a flight coating of glue, is pointed out as a great advantage by the inventor, who 

 likewife informs us that they were ufed in the expedition to Ireland as fignal lanthorns, 

 though contrary to his wiflies. For this ufe he recommends the large plates of mica, 

 which were then imported from Bolton. With the latter fubftance, enclofed between two 

 :pieces of very open wire cloth, he made certain fquares, 26 inches in length and 18 in 

 width, for the light-houfe at Ufhant, which had been damaged by a flock of wild ducks, 

 •that flew through the windows and dafhed out the lights. 



Citizen Rochon affirms, that lanthorns of wire cloth, prepared in his method, are much 

 cheaper than thofe made of tin and horn ; that they are very cheaply repaired, and afford a 

 llronger light. 



He applied coarfe iron wire cloth to another ufe, which, he thinks, may be worth attention 

 in future. He made the roof of one of his workfliops of this wire-cloth in order to avoid 

 the danger of fire, and covered it with a flight coating of plaifter. He thinks that a com- 

 pofition of lime and pounded fcales of iron would have been preferable. This coating 

 ought not to be thicker than a flate ; and he recommends that it (hould be penetrated with 

 boiling whale oil, and painted with tar and ochre. Such a roof would afford no hold for 

 the wind, and might, as he apprehends, be of confiderablc ufe to defend buildings and 

 Iheds which require particular defence againft fire. 



In the courfe of experiments made for the difcovery of a varnifh proper to defend 

 his new lanthorns from moifture. Citizen Rochon did not employ refins or copal, which 

 are always fomewhat friable, but a perfe<n; folution of elaftic gum in drying linfeed 

 oil. This varnifli or unguent having fixed the attention of Genouin, that learned chemifl 

 demanded whether it might not be praiSlicable to ufe it in making bougies and other 

 medical inftruments, which were alfo at that time very much wanted. From this fug- 

 g^ftion, Rochon employed tlie Englifli machine for weaving whips to make the morecon- 

 fiftent part of the inftrument. He plunged this woven piece in a mixture of melted wax with 

 -a little ochre, then drew it through a wire plate to take off the fuperfluous wax, and render 

 it perfedlly fmooth } after which he applied the varnilh of elaftic gum, which completed 

 the inftrument. 



Sartori, ornamental painter at Breft, pointed out to our operator that fi(h glue is pre- 

 ferable to parchment fizc upon open wire cloth, becaufe it is more tranfparent and ftronger. 



VIII. 



On tie ProduElion of Nitric Jcid by the ContaB of Oxygen very much heated and the Air of the 



Atmofphere*. 



Jl K U L, a celebrated artift at Geneva, having conftru6led and improved the apparatus of 

 Watt for the produflion of the gafes, was employed in obtaining by means of this apparatus 

 the oxygen gas from the black oxide of manganefe, taking care not to clofe the apparatus till 

 the manganefe was red-hot, in order to permit the efcapc of the water and carbonic acid 



* Communicated to Dr. Delamethtrie by J. L. Odier. Journal de Phyfique, iii. N«w Series, p. 4^4. , 



Vol,. II.— Dec. 1798. 3H wEUh 



