1834.] Miscellaneous. 479 



der taken for use. With this is used also the best white cotton of Loo Chow, ten 

 times bowed (or bolted), and the very light cotton which is uppermost taken for 

 use. 



Rice-water, made from the whitest rice, being mixed with these two ingredients, 

 the whole is taken up with a mould made of bambu screen of the size required, 

 and then applied to heated wall to dry. 



This forms the whitest and finest Kiug Yuca paper. 



The above notes were accompanied by seven outline drawings, made in China, 

 of the various processes of manufacturing paper from the bambu, which drawings» 

 by the liberality of Mr. Reeves, have been placed in the Society's Library. 



2. — Preventing the Adhesion of Earthy crust to the Inner Surface of Steam Boilers. 

 [From the Trans. Soc. Arts, xlix. pt. 2.] 



Almost all natural waters hold in solution both carbonate and sulphate of lime, 

 two earthy salts, of which the former is thrown down by bringing the water to a 

 boiling beat, and the latter by evaporation. On this account it is, that if the inside 

 of a steam-engine boiler be examined, after having been in use for a few days, 

 jt will be found to contain muddy water, and an earthy crust will be seen adher- 

 ing to the iron plates of which the vessel is formed. The rate at which this 

 crust is deposited depends on the harduess of the water employed, that is, on the 

 proportion of the above-mentioned earthy salts which it contains. This crust is a 

 much worse conductor of heat than iron is, and, therefore, a boiler lined with it, 

 even to the thickness of the tenth of an inch, possesses the following defects. The 

 water which it contains ii not so soon brought up to the boiling point, and a 

 greater quantity of fuel is required to produce a given quantity of steam, because 

 a large proportion of the heat given out during its burning is carried up the chim- 

 ney and lost. It becomes, therefore, necessary, from time to time, to remove 

 this crust, which is naturally done by a hammer and chisel ; but this operation not 

 only incurs a waste of time, but the boiler is often seriously injured, and rendered 

 leaky by means of it. 



It has been found, if a few potatoes are thrown into the boiler when it is again 

 filled, after having been cleaned out, that the formation of crust is sensibly re- 

 tarded, and that the adhesion of it to the sides of- the boiler is greatly weakened, 

 so as to allow of its being detached more speedily, and with much less hazard. 



Another method of producing the same effect has been pointed out to the Society 

 by Mr. James Bedford, of Leeds, druggist. He put into a large steam boiler be- 

 tween two and three gallons of sperm oil foots ; and found that, after eight weeks 

 constant use, the deposit of crust was very small compared to what it used to be 

 from the same water alone, and also that the crust could be cleared otf by means 

 of a common stiff broom. The application of oily matters for this purpose, 

 though original on the part of Mr. Bedford, is not absolutely new ; for the Soci- 

 ety have been informed by one of their members, that he has known an iron boil- 

 er using Thames water preserved in constant use for seventeen years by cleaning 

 it often, and smearing the inside with oil or tallow after each cleaning. 



The Society, however, have reason to believe that neither of the above methods 

 are in common use, and have, therefore, directed this short statement to be pub- 

 lished for the benefit of those whom it may concern. 



