12 



NA TURE 



[November i, 1900 



In the Geological Series, Vol. i., No. 7, of the Field 

 Columbian Museum publications, Dr. O. C. Farrington de- 

 scribes some new mineral occurrences in America. These 

 include, amongst others, the rare inesite from a mine near Villa 

 Corona, Mexico, a mineral which is only known from three 

 other localities in the world ; also some curious crystals of 

 golden calcite from the Bad Lands region, which exhibit such 

 distortion as to have an apparent prismatic form. There is an 

 interesting note also on the use of dolomite as money by 

 the Pomo Indians, inhabiting Lake County, California. The 

 •dolomite money is fashioned by cutting symmetrically-shaped 

 cylindrical pieces from the rough pebbles. These are afterwards 

 burned to bring out streaks of a reddish colour and are then 

 polished and perforated. It is stated that a well-worked piece 

 is estimated at almost the value of its weight in gold. A second 

 section of this publication deals with some interesting crystal 

 forms of calcite from Joplin, Missouri, which are remarkable 

 " not only for their size, but for their transparency, varied colour 

 and the perfection of their crystal form." The paper is well 

 illustrated. 



In an article on "The Orange River Ground Moraine" 

 iTrans. S. African Phil. Soc. vol. xi. part 2, September 1900), 

 Messrs. A. W. Rogers and E. H. L. Schwarz describe the glacial 

 characters of the Prieska conglomerate which occurs beneath the 

 Kimberley shales. In their opinion it is a true till formed by 

 4and-ice ; numerous strice are to be found on the boulders, 

 while the rock-surfaces underlying the conglomerate are clearly 

 glaciated. A number of photographic plates support the con- 

 clusions of the authors. They remark that the relationship 

 -between the Prieska conglomerate and that known as the Dwyka 

 conglomerate is still uncertain. The Dwyka conglomerate forms 

 the base of the Mesozoic group, and has long been regarded as 

 •of glacial origin. An important paper on the chemical compo- 

 sition of the soils of the south-vveslern districts of Cape Colony 

 is contributed to the same publication by Mr. Charles F. Juritz. 

 Prof. W. M. Davis announces {Appalachia, vol. ix., March 

 .1900) that his doubts as to the ability of ice to erode deep 

 valleys and basins have been dispelled by a study of the valley 

 of the Ticino, towards St. Gotthard. The fact that the side 

 •valleys open into the main valley several hundred feet up, indi. 

 ■cates that the ice-stream, while deepening the main channel, 

 ■rose high enough to prevent the small lateral glaciers from exer- 

 •cising much erosive power on their courses. In a second article 

 {Proc. Boston SocNat. Hist., vol. xxix., July 1900) Prof. Davis 

 pursues the subject of "Over-deepened main valleys and hang- 

 ing lateral valleys," and deals also with the excavation of lake- 

 'basins by ice -action. 



The well-known formula for the velocity of propagation of 

 capillary waves or "ripples" shows that the surface-tension of 

 a liquid can be determined experimentally by observing the 

 wave-length and velocity, or the wave-length and frequency of 

 such waves. Dr. Leo Grunmach, of Berlin, has successfully 

 applied this method to liquids, and he now communicates to the 

 Sitzungsberichte of the Berlin Academy an account of deter- 

 minations of the capillary constants of liquefied gases by the 

 same method. The waves are excited by a tuning-fork with 

 needle points dipping into the liquid, and the interference-curves 

 enable the wave-lengths to be measured with considerable accu- 

 racy. The method has been applied to liquefied sulphurous 

 acid, Pictet's fluid (a mixture of 64 parts by weight of sul- 

 phurous acid with 44 parts carbonic acid), liquefied ammonia and 

 liquefied chlorine, and the values of the capillary constants will, 

 it is surmised, lead to interesting results in connection with 

 critical point investigations. 



The smallest lateral difference of place that is just visible has, 

 until recently, been given as about 50" to i' angular measure. 

 The method employed by Helmholtz and others in reaching 



NO. 16 1 8, VOL. 63] 



this result was the well-known one of bringing two parallel 

 lines together until they finally are just distinguished as two. 

 Prof. George M. Stratton, writing in the Psychological Review 

 for September, describes a different method by which it is now 

 evident that a lateral difference of place of about 7" of arc can 

 be directly perceived. Instead of using lines or points side by ^ 

 side, the experiments which gave this result we're made with ; 

 lines end to end, so arranged that the upper of two perpendiculars 

 could be moved at will to the right or left, while still remaining 

 exactly parallel to the lower line. The observer had simply to 

 judge whether the upper line was continuous with the lower or 

 to which side it was displaced. The results, which gave 7" as 

 the threshold of space distinction under these conditions, are 

 interesting, as explaining Bourdon's experiments, according to 

 which a difference of position amounting to but 5" gives a 

 perceptible stereoscopic effect. 



Mr. Frank B. Williams contributes to the Proceedings of 

 the American Academy of Arts and Sciences a paper on the 

 geometry on ruled 'quartic surfaces. Of the quartic scrolls 

 Cremona enumerates twelve, while Cayley divides these scrolls 

 into ten species, stating that Cremona's two remaining species, 

 though properly considered as distinct from the others, may be 

 regarded as sub-forms of his seventh and ninth species. These 

 two are the developable quartic or torse, whose edge of regres- 

 sion is a twisted cubic, and the quartic cones. It is the purpose 

 of Mr. Williams's paper to consider the classification of curves 

 on all ruled quartic surfaces, to find the formula for the number 

 of intersections of any two curves that lie on the same ruled 

 quartic surface, and to point out some of the most notable 

 results obtained in the course of the investigation. The equations 

 of many of the ruled quartic surfaces are so complicated that 

 very serious difficulties arise when we attempt to treat them 

 analytically, and the author finds it convenient to employ the- 

 synthetic method of Prof. Story. 



Mr. F. J- Rogers, in the August number of the Physical 

 Review, advocates the use of the M.K.S., or metre-kilogram- 

 second, system of units in solving problems in mechanics where 

 solutions involving the C.G.S. units of force and work lead to 

 enormously large numerical measures. The author remarks that 

 the common mode of abbreviating these large numbers by using 

 powers of ten gives some trouble to beginners. Mr. Rogers 

 suggests that the corresponding absolute unit of force may be 

 called the large dyne, or the Dyne spelt with a big D ; but this 

 nomenclature seems capable of improvement in order to avoid 

 confusion with the megadyne, which contains ten of his large 

 dynes. 



A series of interesting experiments on the explosive effects 

 of the modern infantry bullet have been carried out in Germany 

 by C. Cranz and K. R. Koch. They used a new Mauser rifle 

 of 6 mm. bore, having a muzzle velocity 100 m. greater than 

 " Model 88." To imitate the effect upon large blood-vessels, 

 while at the same time obtaining simple physical conditions, the 

 experimenters constructed short hollow tin cylinders filled with 

 water, and closed at one end with a sheet of rubber, and at the 

 other with a sheet of parchment paper. Electrodes were 

 mounted before or behind the cylinders, or inside them, and the 

 discharge spark produced by the bullet was utilised to obtain 

 a photograph of its silhouette at various points of its path. 

 Among the important facts thus elicited it appears that the body 

 struck is not displaced by the entry of the bullet. On leaving 

 the body, the bullet carries away with it a small part of the hind 

 surface, having a small round perforation through which the 

 bullet passed. The "explosion" does not take place until the 

 bullet has left the body. . After discussing the evaporation, 

 hydraulic-pressure, rotation, and sound-wave theories of the 

 explosion, and discarding them all, the authors conclude that 



