312 



SCIENCE 



[N. S. Vol. XXVI. No. 662 



tained. Condensation products of Chloral 

 with the three nitranilines, p-bromaniline, 

 o-toluidine, anthranilic acid, and o-anisidine 

 were prepared. By-products, as yet uniden- 

 tified, were obtained with o-toluidine and with 

 anthranilic acid. The condensation products 

 are readily broken down by hydrochloric acid 

 and by acetic anhydride. When suspended or 

 dissolved in the glacial acetic acid they react 

 with extreme smoothness with bromine, form- 

 ing beautifully crystalline compounds which 

 are much more stable than the condensation 

 products. 



Chapel Hill Ferns: W. 0. Cokee, of the Uni- 

 versity of North Carolina. 

 A collection of the living ferns and fern 

 allies native to Chapel Hill, N. C, was made 

 and exhibited in pots. Twenty species were 

 represented, including all the known Pterido- 

 phytes of the neighborhood, except Boiry- 

 chium ternatum and its variety, dissectum, 

 which had not yet appeared above ground. 



Notes on Turtles of Genus Pseudemys : C. S. 

 Brimley, of Raleigh, N. C. 

 This paper discusses the character of the 

 turtles of this genus and shows that the dis- 

 tinctive characters attributed to P. hiero- 

 glyphica, P. Latyrinthica, P. moiilensis and 

 P. Conclnna all fall within the limits of in- 

 dividual variation of the last named form. 

 These conclusions are drawn from an exami- 

 nation of all specimens of the genus that have 

 passed through the author's hands for the 

 last five or six years. 



Electricity in Heavy Traction (illustrated by 

 lantern slides) : J. E. Latta, of the Uni- 

 versity of North Carolina. 



The Design of High Masonry Bams: Wil- 

 liam Cain. 



The claim is made that in addition to the 

 three universally imposed conditions, no ten- 

 sion, safe unit pressures and no possible sli- 

 ding at any horizontal joint, a fourth condi- 

 tion must be imposed, viz., that the factors 

 of safety against overturning and sliding shall 

 increase gradually from the base upward, to 

 allow for the proportionately greater influence, 

 on the upper joints of the wind and wave 

 action, floating ice or other bodies, and espe- 



cially of the great forces caused by the ex- 

 pansion of thick ice under an increase of 

 temperature, and by earthquakes. 



It was found that this could easily be done 

 by taking the well-known theoretical triangu- 

 lar type of cross-section of dam and making 

 some additions at the top sufficient for a 

 roadway. 



A preliminary design is given for a dam 

 258 feet high, with factors of safety and unit 

 pressures marked on the drawing, satisfying 

 all four conditions, the area of cross-sec- 

 tion and height being the same as for the 

 celebrated Quaker Bridge design. A compari- 

 son was instituted unfavorable to the latter, 

 in that its factors of safety are too small, 

 particularly in the upper portions, where by 

 the proposed fourth condition they should be 

 largest. 



This criticism owes its significance to the 

 fact that the new Croton Dam, of New York, 

 224 feet high to water surface and finished 

 February 1, 1906, at a cost of over $7,500,000 

 has a profile for 224 feet in depth, exactly 

 the same as the quaker bridge design for the 

 same depth. 



The Optical Rotation of Volatile Oil: C. H. 

 Herty and G. A. Johnson, of the Uni- 

 versity of North Carolina. 



Children's Home Society Methods: Wm. B. 

 Streeter, of Greensboro. 



Gametophytes of Botrychium Virginianum: 

 Raymond Binford, of the University of 

 North Carolina. 



They were found in moist oak woods under 

 the leaves. Some were almost on the surface 

 of the soil, while others were imbedded one 

 to two inches in the soil. They seem to have 

 gotten down by means of worm holes or cracks 

 made by roots of trees. Sizes ranging from 

 2 mm. to 10 mm. were shown. Specimens of 

 these plants were exhibited before the 

 academy. F. L. Stevens, 



Secretary 



DISCUSSION AND CORRESPONDENCE 



SEEING THE LIGHTNING STRIKE 



On July 14, 1907, at about 5:30 p.m., for 

 the first time in my life, I saw the lightning 



