Febbuaky 25, 1910] 



SCIENCE 



'319 



these standard solutions to students as " un- 

 known " bottles; these consist of homoeopathic 

 vials of 50 CO. capacity. For the analysis the 

 student takes 25 e.c. of his solution, the other 

 half being reserved in case of accident. 



The amounts of standard solutions pipetted out 

 should be such as to yield a suitable concentration 

 when the volume is diluted to 50 c.c, i. e., when 

 the bottle is filled. 



Example : Pipetted out into " unknown " bottle : 

 1 CO. NaCl sol, 2 c.c. CalNOs),, 1 c.c. NH,N03, 

 and then fill the bottle with distilled water. 



Since the student uses only 25 c.c. of this solu- 

 tion the latter will contain: 50 mgs. Na, 100 mgs. 

 Ca, 50 mgs. NH,. 



The following papers were reported by title: 

 Conditions under which Secondary School Teach- 

 ers Conduct their Work: Albert L. Smith. 

 Conditions and Equipment in Secondary Schools : 



Chables R. Allen. 

 Elementary Chemistry Teaching as a Means of 

 Developing the Power of Independent Scientific 

 Reasoning: Arthxjb A. Blanchaed. 

 The First Course in Chemistry for Secondary 

 Schools: M. D. SoHON. 



D. L. Rais'dall, 

 Press Secretary 



SOCIETIES AND ACADEMIES 



the geological society of WASHINGTON 



At the 225th meeting of the society, held on 

 Wednesday, January 12, Mr. Fred. E. Wright 

 exhibited specimens of obsidian from Hrafntin- 

 nuhryggur, Iceland, with peculiarly pitted sur- 

 faces, resembling the markings of the Austrian 

 moldavites; also a unique type of crystallization 

 of radial spherulites in cavities of that obsidian. 



Mr. David White exhibited a photograph of an 

 unusually large and complete Stigmaria stump, 

 taken in an anthracite mine near Seranton. Pa. 



1 1 afforded an excellent illustration of a " kettle 

 bottom " or " pot," a common source of danger 

 in coal mines, and clearly showed the hole in the 

 roof above the fallen stump. 



Mr. Chas. Butts described a Carboniferous coal 

 bed overlain by Lower Cambrian limestone, near 

 Aldrich, Ala., the limestone being thrust over the 

 coal at the fault bounding on the east the Carbon- 

 iferous rocks of the Cahaba trough. The coal is 

 completely overturned, lies flat at the exposure, 

 and is unchanged except for being crushed and 

 mixed with shale. 



Regular Program 

 Influence of the Earth's Rotation on the Lateral 



Erosion of Streams: H. M. Eakin. 



Observations on Alaska rivers indicate a 

 higher efficiency of the deflective force of the 

 earth's rotation in determining lateral erosion of 

 streams than has been ascribed to it. The Yukon 

 River and its tributaries, the Tanana, Koyokuk 

 and Innoko, and the Kuskokwim, all large Alaska 

 streams, show a marked predominance of erosion 

 on the right bank. The strength of the deflective 

 force as computed and compared at different latir 

 tudes shows it to be much stronger in the higher 

 latitudes. For instance, for latitudes 5°, 25°, 

 45° and 65°, the ratios are approximately 1 to 

 4.8 to 8.0 to 10.3. The eflTectiveness of the de- 

 flective force may be compared with that of the 

 centrifugal force of various curves of rivers, that 

 of the deflective force at latitude 65° being ap- 

 proximately equivalent to that of the centrifugal 

 force developed on a curve having a radius of 0.2 

 miles, computations being based on an assumed 

 velocity of 2 meters per second. The lateral 

 stresses due to either centrifugal force or de- 

 flective force tend to establish cross gradients 

 which would oppose them. The lateral stresses 

 being weaker in the lower part of the stream, the 

 stronger lateral gradient supported by the upper 

 part of the stream sets up an undertow in a 

 direction opposite to that of the lateral stresses. 

 The results of the boring currents thus produced 

 are expressed in selective cut and fill. The de- 

 flective force being to the right in the northern 

 hemisphere combines with the centrifugal force 

 on right curves and opposes it on left curves. On 

 straight reaches the deflective force acts alone. 

 In a meandering stream the lateral gradients are 

 reversed on successive bends and the lateral 

 stresses are not fully expressed in lateral currents, 

 since they are under conditions of acceleration 

 much of the time. On straight reaches, there 



