February 18, 1916] 



SCIENCE 



239 



range on the north and connects tlie upper val- 

 leys of Chulitna and Susitna rivers. liTenana 

 Eiver, a tributary of tlie Tanana, occupies the 

 eastern part of the region. The valley of Jack 

 Eiver, which crosses Broad Pass just above 

 the narrow valley of the Nenana, before that 

 stream passes through the Alaska range, pro- 

 vides the route by which the railroad will 

 cross from the Susitna- Chulitna drainage 

 basin to that of the Tanana. The upper parts 

 of streams tributary to Chulitna and Jack 

 rivers overlap each other within Broad Pass, 

 there being no appreciable divide between, so 

 that the grades from the head of the Chulitna 

 to the head of the Susitna are gentle and 

 there is no obstruction. North and south of 

 Broad Pass are high mountains. Those on 

 the north are part of the great range from 

 which, only 70 miles to the west, rise Mount 

 McKinley and, nearby on the east. Cathedral 

 Mountain and Mount Hayes. There is a fair 

 growth of timber in the larger valleys but most 

 of the country is above timber line. This re- 

 gion has long been a favorite hunting ground 

 for the Indians of the Susitna valley. The 

 geologic conditions in the region appear to be 

 favorable to mineralization, but no valuable 

 ore bodies have yet been discovered. The 

 most favorable reports come from the district 

 just west of Broad Pass, near the head of 

 Chulitna Eiver, an important gold placer 

 district, where prospecting has been carried 

 on for several years. Valdez Creek lies 

 about thirty miles east of the pass. Along 

 some of the streams between Broad Pass and 

 Valdez Creek there are prospects of placer 

 gold, which, however, has not been found in 

 commercial quantity. Copper prospects, too, 

 have been discovered in several parts of the 

 region, and at one place, Coal Creek, there Is 

 a small area of coal. The railroad, which will 

 probably soon reach this region, will aid 

 greatly in its development. The wealth of the 

 Broad Pass region appears to be mineral 

 rather than agricultural, and it can be profit- 

 ably esploited only by a greater population 

 and through better means of transportation. 



At the meeting of the Eoyal Society on 

 liTovember 11 Sir Eonald Eoss read an intro- 



ductory paper on " Pathometry." According 

 to an abstract the method he proposed to fol- 

 low in studying the nature of the functions 

 according to which the number of individuals 

 infected with some disease should vary from 

 time to time, on the supposition that the laws 

 governing the rate of transference of the con- 

 sidered disease were already known a priori. 

 He stated the fundamental problem under con- 

 sideration in the following terms : " If a popu- 

 lation is divided into two groups, namely, those 

 who are aSected by some kind of happening, 

 such as an infectious disease, and those who 

 are not so affected; and if in unit of time a 

 constant or variable proportion of the non- 

 affected become affected, while simultaneously 

 a constant proportion of the affected become 

 non-affected (that is, revert or recover) ; and 

 if at the same time both the affected and the 

 non-affected are subject to different birth-rates, 

 death-rates and rates of immigration and of 

 emigration, so that the whole population may 

 be incessantly varying during the period 

 under consideration; then what will be the 

 number of affected individuals and also the 

 niunber of new cases at any moment during 

 that period ? " In this first paper the problem 

 was presented in mathematical language, with 

 its solution, and a broad analysis of the curves 

 obtained and of some integrals. Only con- 

 stant rates of happening (applicable to other 

 happenings besides disease), and rates which 

 varied according to the number of individuals 

 already affected (specially applicable to infec- 

 tious diseases) were considered. In the latter 

 cases the resulting curves were frequently bell- 

 shaped, declining a little more slowly than 

 they rose — that is, generally similar to the 

 curves frequently seen in epidemics — thus sug- 

 gesting prima facie that epidemics might be 

 largely explicable in the terms of the thesis 



UNIVERSITY AND EDUCATIONAL 

 NEWS 



The General Education Board announces 

 appropriations to colleges as follows: Mary- 

 ville College, Maryville, Tennessee, $75,000 

 toward an endowment fxmd of $300,000 ; "West- 



