LIME AITD CEMENT IISTDUSTKIES 741 



insure a fair exponent of the quality, and store tlie same in tightly 

 closed receptacles impervions to light or dampness nntil required 

 for manipulation, when each sample of cement should be so thor- 

 oughly mixed, by sifting or otherwise, that it shall be uniform 

 in character throughout the mass. 



SIEVES 



For ascertaining the fineness of the cement, it will be con- 

 venient to use three sieves, viz: 



Iso. 50 (2500 meshes to the square inch), wire to be no. 35 

 Stub's wire gage. 



X'O. 74 (5476 meshes to the square inch), wire to be of no. 37 

 Stub's wire gage. 



'No. 100 (10,000 meshes to the square inch), wire to be of no. 

 40 Stub's wire gage. 



The object is to determine by weight the percentage of each 

 sample that is rejected by these sieves, with a view not only of 

 furnishing the means of comparison between tests made of dif- 

 ferent cements by different observers, but indicating to the 

 manufacturer the capacity of his cement for improvement in a 

 direction always and easily within his reach. Tests for strength 

 should be applied to the cement as offered in the market, as well 

 as to that portion of it which passes the no. 100 sieve. 



For sand, two sieves are recommended, viz: 



No. 20 (400 meshes to the square inch), wire to be of no. 28 

 Stub's w^ire gage. 



No. 30' (900' meshes to the square inch), wire to be of no. 31 

 Stub's wire gage. 



These sieves can be furnished in sets, as follows, an arrange- 

 ment having been made with a manufacturer of such articles, by 

 which he agrees to furnish them of the best quality of brass wire 

 cloth, set in metal frames, the cloth to be as true to count as it 

 is possible to make it, and the wire to be of the required gage. 

 Each set will be inclosed in a box, the sieves being nested. 



Set A, three cement sieves, to cost $4.80: 

 No. 100 7 inch diameter: 



No. 74 6i 



No. 50 6 



Set B, two sand sieves, to cost $4: - 



No. 30 8 inch diameter . " ' " 



No. 20 7i '~ i 



