m:\v TORE mail MUSEUM 



\M> \i;i> BAND 



The question of i Btandard Band -rem- one of great importance, 

 f<»r it has been found that Bands Looking alike and Bifted through 

 the Bame sieves give results varying within rather wide Limits. 



The material that Beema likely to give the best resulta is the 

 crushed quartz used in the manufacture of Bandpaper. It is a 

 commercial product, made in large quantities and of standard 

 tirade-. ;m«l can be furnished of a fairly uniform quality. It is 

 clean and sharp, and, although the present price is somewhat 



tessive (3 cents per pound), it is believed that it can be fur- 

 nished in quantity for about $5 per barrel of 300 pounds. As 

 it would be used for tests only, for purposes of comparison with 

 local Bands, and with tests of different cements, not much of it 

 would be required. The price of the German standard sand is 

 about (1.25 per 112 pounds, but the article, being washed river 

 sand, is probably inferior to crushed quartz. Crushed granite 

 can be furnished at a somewhat loss rate than quart/, and crushed 

 trap for about the same as granite, but no satisfactory estimate 

 has been obtained for either of these. The use of crushed quartz 

 is recommended by your committee, the degree of fineness to be 

 such that it will all pass a no. 20 sieve and be caught on a no. 30 

 sieve. Of the regular grade, from 15# to 37^ of crushed quartz, 

 ii". :; passes a no. 30 sieve, and none of it passes a no. 50 sieve. 

 As at present furnished, it would need resifting to bring it to 

 the Btandard Bize; but, if there were sufficient demand to warrant 

 it. it could undoubtedly be furnished of the size of grain required 

 at little, if any, extra expense. 



A bed of uniform, clean -and of the proper size of grain has 

 not been found, and it i- believed that to wash, dry, and sift any 

 of the available Bands would so greatly increase its cost that the 

 product would not be much cheaper than the crushed quartz, and 

 would be much inferior to it in sharpness and uniform hardness 

 of particl 



MuT.DS 



The molds furnished are usually of iron or brass, the price of 

 the former being ind of the latter $3 each. Wooden molds, 



if well oiled to prevent their absorbing water, answer a good 

 purpose for temporary use, but speedily become unfit for accu- 

 rate work. A cheap, durable, accurate, and non-corrodible mold 

 i- much t«. be desired. Molds are made for holding one, two or 

 more briquets. A common i'<>nn is shown in pi. 27. 



