494 



NATURE 



[June 24, 1909 



were taken by Prof. Benjamin W. Snow, of Wisconsin 

 VniviTNilv. One of the more elaborate ice-flowers 

 that form on the surface of freezinj^ water is illustrated 

 in V\\i- 5. Mr. Bentley closes his paper with an in- 

 lerestinj^ discussion of the occurrence and ciuse of hail 

 in both suminer and winter, and of the structure of 

 liailstones. Hailstones have various shapes ; they are 

 commonly round, but eg^- and pear-shapes are not 

 rare. They invariably contain air-tubes and bubbles; 

 a typical arrangement, shown by a stone which fell in 

 the winter of 1906-7, is depicted in Fij:;. 6. 



ThanUs to Mr. Bentley, it is now possible to compare 

 and study every variety of snow, frost, :md ice crystals, 

 and the way is clear for the next step, viz. to deter- 

 mine the factors and the conditions governing the 

 several forms. It is strange how little is precisely 

 known of the crystalline form of what in its three 

 different phases is one of the most familiar, necessary, 

 and conspicuous substances in nature. The system is 

 undoubtedly hexagonal, possibly hemimorphic; but the 

 axial ratios quoted in niineralogical text-books are 

 based merely upon exceedingly rough observations 

 made by Nordenskiold on some snowllakes which fell 

 during the severe winter of 1S60. 

 So far as we are aware, no crystal 

 of water has yet been measured with 

 a goniometer, and there is an oppor- 

 tunity for a crystallographer zealous 

 enough to invade a refrigerator for 

 the purpose of measuring a crystal 

 grown under conditions that have 

 been kept as uniform and as favour- 

 able as possible. In the course of 

 his paper Mr. Bentley comments 

 upon the curious changes that have 

 often occurred during the growth 

 of certain of the crystals. For in- 

 stance, in Fig. I the crystals were 

 at first narrow, but afterwards 

 became broad and well-defined. 

 This phenomenon may probably be 

 explained as due to a change from 

 the labile to the metastable con- 

 dition. As Principal Miers has 

 shown, in the labile condition the 

 Srowlh is rapid, and the crystals 

 are narrow and ill-formed; whereas 

 in the metastable condition the 

 i;rowth is slow, and tlie cryst.-ils are 

 larpe and well-formed. We antici- 

 pate that experiments conducted inider conditions of 

 humidity and temperature which were accurately deter- 

 mined would be productive of results of considerable 

 interest. It is clearly impossible to be sure of the tem- 

 perature of a window even when those of the room and 

 of the outer air z re known ; a slight gust of wind might 

 cause a lowering of some degrees. G. F. H. S. 



WWIER POWER IN THE UNITED STATES. 

 T N many of the States of North .America water is 

 ■*• regarded as one of the most valuable of the 

 natural resources. Unlike timber or minerals, it is 

 inexhaustible, and so loop as the rain continues to fall 

 the water resources are beinj^ continually replenished. 

 This fact has been more fully realised since the trans- 

 mission of power to lonj; distances has become 

 practicable owing to the development of electricity. 



The State of Wisconsin is probably as favourably 

 ■iiluated as any of the States with reference to its 

 water power. Realising this fact, the legislature, in 

 conjunction with the Geological Department of the 

 I'nitcd .States, undertook the surveying of the rivers 

 of the Stale and the investigation of their adaptability 

 NO. 2069, VOL. 80] 



I to the generation of power. Six hundred miles of 

 j rivers have already been surveyed, and the results 

 recorded in a report issued by the Wisconsin Geo- 

 logical .and Natural History Department. 



This report slates that at the time of its publica- 

 tion water-power installations to the extent of 130,000 

 horse-power had been developed, this being only a 

 small instalment of the resources of the rivers. 



The average grade of the water surface of the 

 rivers surveyed varies from 3 to 8 feet per mile. 

 The average yearly rainfall is 32*30 inches. Dry 

 periods occur in cycles of about twenty-five years, 

 when the r.iinfall drops to 24*20 inches, and exception- 

 ally dry periods occur about once in fifty years, when 

 the lowest r.'iinfall recorded was i3'5o inches. Owing 

 to the storaj^e cITects of lakes and swamps, the 

 low-water run-otT is as high as 03 to o'S foot 

 per square mile of the drainage area. The cutting 

 down of the forests is, however, having a consider- 

 able effect on the yield of the rainfall ; where clear- 

 ances have been carried out the rain being less ab- 

 sorbed by the soil and the water reaching the streams 

 more quickly. 



The Fox River J".ipcr Com|).inys Mills, Applcion, Wis. Middle Dam. 



The most important purposes to which the water 

 power is applied .are the paper and woollen mills 

 and for electric light and traction. .An example of 

 the extended use of water power for generating elec- 

 tricity is to he found in the works of the small town 

 of Kilbourn, nn the \\'isconsin Kiver, and its distribu- 

 tion to pl.icis 50 miles distant. On the Saint Croix 

 River, where a fall of 50 feet is available, the power 

 developed is equal to 27,000 horse-power, and the 

 transmission ixiends to a distance of 40 miles. The 

 instalment on the Saint Louis River, when fully 

 developed, will he equal to 200,000 horse-power, and 

 the distance <4 transmission 75 miles. This instal- 

 ment, wh<-n in full working order, will only be second 

 to the grc.it hydr.iulic plants at Niagara. On the 

 Fox River ih. re .ire three dams, and water power 

 is supplied in ., Large number of paper and pulp fac- 

 tories, and ;ils(i for factories and electric light and 

 traction, tin- ..trgregate power being equal to 

 35,000 horse-p. wer. The illustration, taken from 

 the report of the Wisconsin Geological Depart- 

 ment, gives some idea as to the extent of the 

 factories the works of which are actuated by water 

 power. 



