Febeuabt 25, 1910] 



SCIENCE 



307 



have been most marked in the southwestern part 

 of the area, not far from the Virunga group of 

 volcanoes of Lake Kivu. Five main blocks may 

 be recognized which are separated by troughs; 

 the islands of the western coast of the Victoria 

 Lake present the first of these, while three others 

 range one behind the other between the lake shore 

 and Valley of the Kagera, and in the intervening 

 troughs lie lakes, swamps or slowly flowing rivers ; 

 the fifth forms the Ruanda Plateau west of the 

 Kagera. The edges of these blocks have as yet 

 been but little modified by weathering, so that the 

 latest movements would appear to be compara- 

 tively recent. 



The formation of Victoria Lake is shown to 

 be due to mutual adjustments among these 

 earth blocks, separated as they are by great 

 faults running in the directions IST.-S., E.-W., 

 NE.-SW., and in the area south of the lake 

 also NW.-SE. Again quoting Lyons : 



Large masses, many kilometers long, have been 

 raised, lowered or tilted, and in the valleys formed 

 along the fracture lines, the main drainage lines 

 of the district run. Lake Victoria itself is out- 

 lined by such fractures. 



All writers seem to agree upon the domi- 

 nance of block movements of the crust in de- 

 termining the relief of Central East Africa, 

 and it is therefore interesting to learn from 

 these newer studies of the Nile Basin, that the 

 great river itseH between Korusko and Aswan 

 (Assouan) wherever crystalline rocks occur in 

 its neighborhood, takes directions parallel to 

 the neighboring intrusive dikes. 



While the region is one of earthquakes, the 

 movements disclosed by the series of gauge 

 readings would seem to be of the slower type, 

 and it would be of great interest to know 

 whether the main periods of change of level 

 correspond in time to any subterranean rumb- 

 lings such as are now being reported from so 

 many unstable districts and are called hron- 

 tidi. As compared with the crustal move- 

 ments which are revealed by gauge readings 

 within the Laurentian Lake district of North 

 America, these African observations differ in 

 being more rapid, and, further, in indicating 

 reversals in the direction of movement. They 

 similarly, however, point the moral that the 

 sensitiveness of great inland bodies of water, 



when employed as precise levelling instru- 

 ments, has never been properly appreciated. 

 Wm. H. Hobbs 

 Univeesitt of Michigan, 

 Ann Abboe, 



January 29, 1910 



TBE FORTY-FIRST GENERAL MEETING OF 

 THE AMERICAN GBEMICAL SOCIETY. II 



DIVISION OF FEETILIZEE CHEMISTET 



P. B. Carpenter, Chairman 

 J. E. Breckenridge, Secretary 

 The Direct Estimation of all Intensities of Hydro- 

 gen Ion Concentration by Means of Di-nitro- 

 hydrochinone : Laweence J. Henderson. 

 The Nitrogen Thermometer from Zino to Palla- 

 dium: A. L. Day and K. B. Sosman. 

 Laboratory Methods for Organic Nitrogen Avail- 

 ability: C. H. Jones. 



The alkaline permanganate and pepsin methods 

 for determining organic nitrogen availability as 

 used in the Vermont Experiment Station labora- 

 tory are described. Results by these methods on 

 fifty-one high- and low-grade animal and vegetable 

 ammoniates now on the market are tabulated and 

 briefly commented upon. 



Both methods have been used at the Vermont 

 Station on officially collected commercial fertil- 

 izers for the past twelve years. Tables were 

 shown giving the results of this work. 



The writer concludes that the alkaline perman- 

 ganate method, while empirical, is nevertheless 

 valuable to eliminate quickly from a large num- 

 ber of samples those of questionable availability 

 which may then be tested by the longer pepsin 

 process and qualitatively to show more in detail 

 the nature of the nitrogen source. 



The following papers are reported by title: 

 Influence of Chemistry on Agriculture: F. B. 



Caepenteb. (Chairman's address.) 

 Concerning After Effects of Certain Phosphates 

 on Limed and Vnlimed Lands: H. J. Wheeleb. 

 New Method for Filtrating Insoluble Phosphoric 



Acid: R. H. Fash. 

 Facts Brought Out Regarding Uniform Analytical 

 Methods for Phosphate Rock through the Recent 

 Work of the National Fertilizer Association's 

 Committee: C. F. Hagedoen. 

 Neutralization of the Ammonium Citrate Solu- 

 tion: J. M. McCanduess. 

 Note on the Determination of Phosphoric Acid by 

 the Official Volumetric Method: F. B. Cab- 

 penteb. 



