May 21, 1897.] 



SCIENCE. 



799 



meters, 3.24 parts, while at the earth's sur- 

 face the amount is 3.03 to 3.20. Nansen 

 found, when crossing Greenland, that at 

 elevations of 2,300-2,700 meters, and with 

 a temperature of -20° , the amount of carbon 

 diosid was as great or even greater than at 

 Stockholm. It seems now well settled that 

 the old figure of 4 per 10,000 as the con- 

 tent of the atmosphere in carbon dioxid is 

 decidedly too large, and that the amount 

 varies locally within quite narrow limits, 

 but with a tendency to increase slightly 

 with the elevation. The cause of this varia- 

 tion is, as yet, unexplained, but the con- 

 sumption of the gas near the surface of the 

 earth by plants would seem to be a factor. 

 A SERIES of experiments on the resistance 

 of cements to sea water was begun in 1856 

 at the harbor of La Eochelle, and is de- 

 scribed in the TJionindustrie-Zeitung by E. 

 Candlot. The experiments consisted in 

 placing cubes of cement of different com- 

 positions, 60 centimeters long, where they 

 would be covered by the sea at high tide 

 and exposed to the air at low water. Blocks 

 of cement without sand disintegrated more 

 rapidly than those containing sand, and the 

 best mixture was one volume of cement 

 with from one to two volumes of sand. 

 Such blocks lasted from twenty to thirty- 

 eight years. This mixture corresponds to 

 the least porous material, that is, the ce- 

 ment sufBces to completely fill the inter- 

 stices between the grains of sand. An ex- 

 cess of lime or magnesia in the cement is 

 detrimental ; this occurs when the quantity 

 of silica and alumina is insufficient to 

 saturate these bases. The best cement is 

 that which requires least water for mixing, 

 relative to the amount which it can hold 

 chemically combined when ' set.' Portland 

 cement was found to require very little ex- 

 cess of water, and hence gave the densest 

 and least porous results and the maximum 

 durability. 



J. L. H. 



SCIENTIFIC NOTES AND NEWS. 

 A PERMANENT CENSUS BUREAU. 



"We are glad to note that Senator Chandler, 

 Chairman of the Committee on the Census, re- 

 ported favorably, on May 10th, the bill providing 

 for taking the twelfth census and for the es- 

 tablishment of a permanent census service. 

 This bill was drawn up by the Hon. Carroll D. 

 D. Wright, Commissioner of Labor, in accor- 

 dance with a joint resolution of Congress, and 

 demonstrates the advantages of securing ex- 

 pert scientific advice in regard to proposed leg- 

 islation. The main provisions of the bill are 

 as follows : 



It provides for a permanent census ofiSce at 

 Washington, the duties of which shall be the 

 taking of the twelfth and succeeding decennial 

 censuses and the collection of other statistical 

 information in intervening years. The Director 

 of the Census and the Assistant Director are to 

 be Presidential appointees, but the latter must 

 be an experienced practical statistician. The 

 other oificers, including five chief statisticians 

 at an annual salary of, $3,000 each, will be ap- 

 pointed under the civil service rules. 



The sum of $75,000 is to be appropriated for 

 the organization of the office. It is estimated 

 that the annual cost will be less than $500,000, 

 and that the decennial enumeration with the 

 tabulation of results will cost an additional sum 

 of about three or four million dollars. The 

 permanent census bureau would consequently 

 cost less than the eleventh census, for which 

 some eleven and a half million dollars were ex- 

 pended. It is estimated by Mr. Wright that 

 two million dollars of this sum can be charged 

 directly to the fact that the force was not under 

 civil service rules. 



The bill provides for taking the census here- 

 after on April 15th in jDlaoe of June 1st, as at 

 the latter date the people are scattered from the 

 cities. It is proposed to omit from the decennial 

 census certain items regarding vital statistics, 

 mortgages, Indians, etc., included in the 

 eleventh census, these being in part relegated to 

 other bureaus and to the separate States. The 

 oflB.ce would, however, issue annually accounts 

 of agricultural products and biennially accounts 

 of manufactures. Statistics of deaths and births 

 would be obtained from the registration records 



