46 



SCIENCE 



[N. S. Vol. XLVII. No. 1202 



thyst of Fujiya, Hoki Province, must b« 

 noted, and rose quartz is found at Gota. 

 Maki Province (pp. 46, 47). Inclusions of 

 quartz come ctieily from Mukaiyama and 

 Takemori, tlie green fibrous inclusions being 

 epidote and tlie brown fibrous ones tourmaline; 

 included sulphur of a beautiful yellow is 

 limited to quartz of Takemori. Fluid inclu- 

 sions are quite common, being usually dis- 

 tributed irregularly throughout the crystal, 

 though sometimes in definite layers parallel 

 to the faces of the rhombohedron (p. 44). 

 Felspar, tourmaline and garnet are here foimd 

 in association with quartz. Localities well 

 known since ancient times for beautiful 

 quartz crystals are the granitic regions around 

 Kimpii-zan, Kai Province. Here colorless and 

 transparent crystals for ornamental work 

 have been obtained for centuries (p. 38). It 

 is well known that the manufacture of beau- 

 tiful crystal balls has long been carried on in 



A small crystal of crysoberyl has been found 

 in stanniferous sand of Takayama, Mino 

 Province; it was of a pale greenish-yeUow 

 color (p. 82). Beautiful crystals of vivianite 

 were at one time met with at Ashio, Shimot- 

 Buke Province. At first they were light blue, 

 but became darker on exposure to the air 

 (p. 86). Some blue, transparent crystals of 

 tourmaline have been found at Takayama, 

 Mino Province, and beryl found here re- 

 sembles the tourmaline in color and form, one 

 end of the crystal being of a lighter hue, 

 while the other end is decidedly darker and 

 only semi-transparent. The topaz, however, 

 is the most conspicuous of the gems foimd in 

 Japan and Dr. Wada gives a very full account 

 both of the occurrences and of the crystallo- 

 graphic forms (pp. 89-113). It occiirs in peg- 

 matite veins in granite as in Takayama and 

 Hosokute, Mino Province, Ishigure, Ise Prov- 

 ince, and Tanokamiyama, Omi Province. 

 Japanese topazes were first exhibited in the 

 National Exposition of Tokio in 187Y. Six 

 different hues have been observed, as foUows: 

 (1) Colorless; (2) wine-yellow, or bluish-yel- 

 low; (3) pale blue; (4) pale brown and pale 

 blue in sectors; (5) pale green; (6) brown. 



On exposure to daylight the brown and 

 brownish-yellow shade into blue, and the blue 

 tends to become colorless. The brown hue is 

 confined to a few freshly-quarried specimens, 

 and is never observable in those which have 

 been kept long in daylight. In some speci- 

 mens the structure is shown by inclusions ar- 

 ranged parallel to the outline of the crystals, 

 producing the strange effect observable in the 

 so-called " phantom quartz." 



The most beautiful of the topaz crystals 

 illustrated by Dr. Wada (Plate XXIV., Fig. 

 a) was found between 1870 and 1880. It 

 came later into the possession of Count K. 

 Inowe who presented it to Dr. Wada. It meas- 

 ures 84 mm. in length, 64 mm. in the longer 

 diameter and 51 mm. in the shorter. It is 

 based on a piece of felspar, and on the side is 

 black quartz crystal, the topaz standing nearly 

 perpendicular to its prismatic faces. 



Geo. F. Kunz 

 New York City 



SPECIAL ARTICLES 



THE GEOMETRICAL MEAN AS A B. COLI INDEX 



Several reasonable objections have dissatis- 

 fied bacteriologists with the present methods 

 of estimating the average number of B. coli 

 in water.^ The following method is proposed 

 as a simple, convenient, and theoretically de- 

 sirable means of arriving at a numerical index 

 representing such a series of results. It was 

 suggested in 1912 by data obtained at the 

 Washington Filter Plant,^ and has since been 

 practically applied with much success. 



Data — B. coli are determined to be present 

 or absent in a series of fermentation tubes 

 containing portions of the sample in multiples 

 of ten, i. e., 10 c.c, 1 c.c, .1 c.c, .01 c.c, 

 .OOlc.c, etc. 



Example: Suppose twenty samples or series 

 of tubes gave the following results, where + or 

 positive means B. coli were found present, 



1 Report of the Committee on Standard Meth- 

 ods, American Public Health Association, 1916. 



2 Wells, W. E., ' ' Some Notes on the Use of 

 Alum in Connection with Slow Sand FUtration at 

 Washington, B. C," Proceedings of American 

 Water Works Association, 1913. 



