Apkil 20, 1883.] 



SCIENCE. 



313 



tive details of the dams and conduits. To give the 

 city 40,000,000 gallons of water daily, it is estimated 

 that the storage-reservoirs on Sudbury River should 

 have a capacity of 4,900,000,000 gallons. So far, 

 three reservoirs only have been built; having a ca- 

 pacity, with that of Farm Pond, of 2,000,000,000 gal- 

 lons, intended to give a supply of 20,000,000 gallons 

 daily to the city. — G. I., v. [646 



Anthracite coal-fields of Pennsylvania. — Mr. 

 Charles A. Ashburner read a paper on a new method 

 of estimating the contents of highly-plicated coal- 

 beds, as applied to the anthracite fields of Pennsyl- 

 vania. The questions of the future production and 

 ultimate exhaustion of these fields are of the greatest 

 importance. In 1860 the population of the United 

 States was 31,44.3,321, and 8,513,123 tons of coal were 

 produced ; i.e., actually shipped to market. In 1870 

 the population had increased twenty-two per cent 

 (38,5.58,371), and the production of anthracite was 

 nearly doubled, being 16,182,191 tons. For the year 

 1880, with a population of over 50,000,000, the product 

 was 23,437,242 -1- tons. In 1882 the actual production 

 was over 30,000,000 tons. It has been variously esti- 

 mated that the 470 square miles containing this coal ' 

 in Pennsylvania will be entirely exhausted in from 

 140 to 204 years. While Mr. Ashburner does not 

 estimate the ultimate exhaustion, he has devised a 

 .method for estimating the contents of these fields 

 from data now being obtained by the careful and 

 practical geological and mining examinations of the 

 state survey. The exact position and detailed struc- 

 tural shape of the coal-beds are first mapped by fifty- 

 feet contour-lines along the floor of the beds, giving, 

 completely and satisfactorily, their geometrical con- 

 struction and shape. These surfaces are then devel- 

 oped into planes by the development into straight lines 

 of the line of the bed, as cut by paralleled section- 

 planes 1,600 feet apart. This graphical method is 

 attended with errors which are mathematically dis- 

 cussed, and wliich have been formulated by Mr. Ar- 

 thur Winslow. This method does not give the true 

 area of the surface of a sphere, cone, or triangular 



TT 



trough. In the case of a sphere, it gives t of -the 



true area; in a cone, the error increases directly as 

 the secant of the angle which the pitch of the cone 

 makes with its axis; and in a triangular trough, which 

 more nearly represents the shape of the anthracite 

 basins, the error is very much less. A practical test 

 has been made of this method in the Panther Creek 

 basin, between Mauch Chunk and Tamaqua; and 

 the maximum possible error in estimating the sur- 

 face-area of the coal-beds was found to be .905 of 1 

 per cent. After the areas are thus found, the con- 

 tents are obtained by careful measurements made in 

 the mines to ascertain the actual number of tons of 

 coal which are contained in a unit (one acre) of bed- 

 area. In this way it has been estimated that the 

 above basin originally contained 1,032,000,000 ± tons; 

 that the area under development originally contained 

 92,000,000 ± tons, out of which latter area .54,000,- 

 000 ± tons have been taken. — (Enij. club Pliilad.; 

 meeting March 17. ) [647 



CHEMISTRY. 

 (Analytical.) 

 Determination of organic matter in potable 

 "water. — In an extended examination of the various 

 methods in use for determining the purity of pot- 

 able water, undertaken by Prof. J. W. Mallet for 

 the National board of health, special attention was 

 given to the ' combustion process ' of Frankland and 

 Armstrong, the 'albuminoid-ammonia' process of 



Wanklyn, Chapman, and Smith, and the 'perman- 

 ganate ' process suggested by Forchhammer. Prof. 

 Mallet finds that it is unsafe to base conclusions on 

 a single determination by the combustion process ; 

 and the evaporation should be conducted by means 

 of steam, in such a manner as to preclude the pos- 

 sibility of absorption of ammonia from the atmos- 

 phere. It was also found advantageous to conduct 

 the evaporation under diminished pressure at quite 

 low temperatures. In the albuminoid-ammonia and 

 permanganate processes the most desirable results 

 were obtained by keeping the volume of liquid in the 

 retort constant and the permanganate in excess. 

 Prof. Mallet thinks that more importance should be 

 attached to the quantity of nitrites and nitrates than 

 is usually assigned to them ; and he finds that they 

 may readily be reduced by phosphorous or hypophos- 

 phorous acid. These methods are regarded by liim 

 as an insufficient basis on which to reach a decision 

 as to the condition of a water ; and they should be 

 made of secondary importance to evidence of a 

 general nature, such as the source and history of the 

 water examined. A thorough biological examination 

 of water polluted in various ways is I'ecommended, — 

 [Amer. chem.journ., iv. 241, 334, 426.) c. F. M. [648 

 Composition of a spring--water from Salz- 

 brunn. — In an analysis of a spring-water from 

 Salzbrunn, in Silesia, T. Poleck obtained the sub- 

 joined results in 1,000 grms. 



Sodium chloride 0,08899 grm. 



" sulphate 0.18010 " 



Potassium sulpbate 0.04085 " 



Sodium bicarbonate 0.87264 " 



Lithium " 0,01140 " 



Calcium " 0.71264 " 



Magnesium " 0,40477 " 



Strontium •' 0.00280 " 



Manganese " 0,00181 " 



Aluminum phosphate 0.00036 " 



Alumina 0.00047 " 



Silicic acid 0.03460 " 



Total 2.23067 gnns. 



Bromine, boracic acid, barium, and nickel were 

 present in quantities too small to be determined 

 quantitatively. The free carbonic acid in 1,000 

 grms. amounted to 849.4 cc, at 10.5°, and 740 mm. 

 pressure. This water would be classified as alkaline- 

 saline, and also as strong sodium-lithium. It con- 

 tains only minute traces of organic matter. — (Journ. 

 prakt. chem., xxvii. 45.) c. F. M. [649 



Origin of arsenic and of lithium in -waters 

 containing calcium sulphate. — In examining 

 different natural waters for arsenic, from Martigny, 

 Bachu, and other localities, M. Sohlagdenbauffen 

 finds it in quantities varying between 0.0050 grm. 

 and 0.0500 grm. per litre. Since arsenic is found in 

 different varieties of gypsum, the author concludes 

 that it is in the form of calcium arseniate. Its 

 origin may be traced to the marls, where it existed 

 as sulphide. By the action of acid calcium carbonate, 

 it was probably converted into the sulpho-arseniate, 

 and finally into the arseniate. When certain marls 

 are submitted to the action of hydrochloric acid, the 

 solution evaporated, and the residue extracted with 

 a mixture of alcohol and ether, lithium may readily 

 be detected by the spectroscope. Five grms. of the 

 earth contain sufiicient lithium to give a distinct 

 red band. — {Journ. pharm. chiin., 1. 464.) c. r. m. 



[650 

 AGRICULTURE. 



Symphytum asperrimum as fodder. — This 

 plant is reported to yield a large quantity of palata- 

 ble and nutritious green fodder, even on poor soil, 



