NOVEMBEB 10, 1916] 



SCIENCE 



687 



that freed the gold from its mother rock and 

 brought about its concentration in prehistoric 

 river channels forms altogether a most im- 

 pressive description of continent building. 

 Looking backward through inconceivably long 

 vistas of time in which periods covering mil- 

 lions of years supplant the centuries by which 

 we now compute its passage, the geologist pic- 

 tures the uplift of the new-born mountain 

 range by upward-forced great bodies of molten 

 granite. This uplift was accompanied or 

 closely followed by the formation of veins and 

 seams of gold-bearing quartz, and the result- 

 ing highland was then planed down by erosion 

 caused by rainfall and the action of streams 

 of water. 



Tracing the long course of this early history 

 the geologist now finds that toward the end 

 of what is known as Tertiary time — a com- 

 paratively recent geologic period — volcanic 

 forces that had long been quiescent vigorously 

 reasserted themselves. Flows of rhyolite, a 

 volcanic rock, pouring from many craters, 

 filled valleys that were covered with gold- 

 bearing gravel, deeply burying the gold and 

 causing the formation of new stream courses. 



The geologic events thus outlined long pre- 

 ceded the period of human history in which 

 these metal deposits were mined. In 1849 an 

 army of gold seekers invaded the Sierra. 

 They worked first along the present streams, 

 but gradually the metal was traced to the old 

 Tertiary river beds on the summits of the 

 ridges and to the quartz veins, the primary 

 source of all the gold in the Sierra Nevada. 

 Millions of dollars in gold were produced 

 annually up to the seventies of the last cen- 

 tury, but the gold-mining industry has slowly 

 diminished, until now less than $1,000,000 is 

 produced annually, the decline being due to 

 the prohibition of hydraulic mining and the 

 exhaustion of the richer channels suitable for 

 drift mining. 



The total output of gold in California is 

 estimated at $1,200,000,000 to $1,500,000,000, 

 about one fifth of which has been derived from 

 quartz veins, $300,000,000 from the Tertiary 

 gravels, and the remainder from the Quater- 

 nary deposits. 



SPECIAL ARTICLES 



ON THE DIFFERENTIAL EFFECT OF CERTAIN 



CALCIUM SALTS UPON THE RATE OF 



GROWTH OF THE TWO SEXES OF 



THE DOMESTIC FOWL 1 



In connection with an extensive series of 

 experiments on the effect of feeding various 

 organ substances to growing chicks, which I 

 have been carrying out during the past 

 summer with the aid of Mr. "W. T. Pettey, 

 two groups were given small daily doses 

 (Ca. 0.1 gm. to 0.3 gm.) of calcium lactate 

 (CaCCJEEjOJ, + 5ILO) and calcium lactophos- 

 phate (a mixture of calcium lactate and cal- 

 cium phosphate containing about 3 per cent, 

 of the latter), respectively. The results were 

 consistent, striking, and in certain particulars 

 entirely new. A complete account of them, 

 with detailed figures, will be published as soon 

 as the material can be prepared for the press. 

 In the meantime I wish to call attention, in 

 a very brief way, to the essential features of 

 the results. The most significant finding is 

 that while neither of these calcium salts affects 

 in any way, in the dosage used, the rate or 

 amount of growth in the male chicles, both of 

 them, but particularly the lactophosphate, in- 

 duce a very marked increase in the absolute 

 amount of growth and a corresponding accel- 

 eration in its rate in the female chicks. The 

 dosage was begun when the birds were 29 days 

 of age and continued until they were 171 days 

 old, after which age there is comparatively 

 little additional growth in the domestic fowl. 

 At the end of this 142-day period the lacto- 

 phosphate females had grown so much faster 

 than the control females that there had been 

 eliminated 58.4 per cent, of the normal differ- 

 ence between the sexes in respect to body 

 weight (secondary sexual character). In spite 

 of the rather large probable errors the abso- 

 lute differences are statistically significant. 

 Thus we have at 171 days of age : 

 Lactophosphate 52 mean wt. ■ — Control 22 mean wt. 

 = 354.6 ± 91.9 gm. 



The difference is 3.85 times its probable error. 



The reproductive organs of the females were 

 stimulated as well as growth. The rate of 



iPapers from the Biological Laboratory of the 

 Maine Agricultural Experiment Station, No. 104. 



