Septembes 18, 1908] 



SCIENCE 



373 



practically constant temperature, compared 

 to the earth's interior; since hy the terms of 

 the hypothesis the soil has heen the seat of 

 living beings during much of the time of 

 cooling. 



Furthermore, the rate of outilow of heat is 

 determined solely by the temperature differ- 

 ence on the two sides of a rock layer, and a 

 cloud envelope could only retard such outflow 

 through materially raising the temperature 

 of the surface rock and diminishing the tem- 

 perature difference on the two sides of the 

 outer zone. This is something which, as 

 shown above, has not taken place, and conse- 

 quently the delivery of thermal energy 

 from the interior to the surface of a cooling 

 earth may be computed for any fraction of 

 its age. The evolution of life must be re- 

 stricted to the later portions of the hypo- 

 thetical cooling process, since, as Lane has 

 pointed out,* rocks seem to have been buried 

 in early times to as great a depth as now 

 without metamorphism, save where mashed 

 or injected. To cite a specific instance — the 

 Belt terrane of Montana and Idaho shows 

 formations which were buried to a depth of 

 several miles in pre-Cambrian times, now 

 almost if not quite as unmetamorphic as the 

 Triassic formations of the eastern United 

 States. 



The actual thermal energy per unit time 

 now and in past times received from the 

 earth's interior, thus computed, could be 

 compared with that determined by measure- 

 ment as received in imit time from the sun 

 and without reference to the actual tempera- 

 tures of either earth or sun. Even in spite 

 of much error in regard to the fundamental 

 constants, unless some surprising error i4 

 previous methods is developed, such a calcu- 

 lation would show the earth to contribute but 

 a negligible fraction and would indicate to 

 what an extent a hypothetical cloud envelope 

 and early atmosphere of assumed composi- 

 tion would have to operate as an impermeable 

 blanket to make up for the hypothetical de- 

 ficiency in solar radiation. Having drawn 

 this thermally opaque envelope about the 



'Science, April 10, 1908, p. 591. 



earth, the Mansonians must next demonstrate 

 how light was able to penetrate to permit the 

 building up of vegetable protoplasm and give 

 employment to the eyes of animals during 

 the Paleozoic and Proterozoic ages. 



Joseph Baerell 



QUOTATIONS 



THE PUBLIC HEALTH 



Professor William T. Sedgwick's address 

 on " The Call to Public Health " has been 

 printed in a recent niunber of Science, and 

 the perusal of it can not fail to be instructive 

 and inspiring. The health of the public must 

 necessarily be based upon the health of indi- 

 viduals, yet when one speaks of the public 

 health he has in mind something much broader 

 and much more important than the health of 

 isolated members of the community. The 

 public health means the health question so- 

 cialized, and this broadening of the base so as 

 to include whole populations has arisen from 

 the conception, made vital by modern science, 

 that the health of the individual immediately 

 concerns his family, his neighbor and his city. 

 There is a community of interests vitally 

 affecting human life which makes the public 

 health of importance to the municipality and 

 the state; and, as Professor Sedgwick easily 

 shows, this is a development that has come 

 very late in modern civilization, and to-day 

 calls for a greater degree of attention than 

 has ever before been given to it. 



A certain selfishness, or indifference to 

 others, that has naturally resulted from the 

 old individualism, has until recent years 

 blinded the majority of people to the neces- 

 sary relation between individual and public 

 health. The main concern of the average man 

 has been to keep himseK and his family well; 

 all others he had no interest in. He paid the 

 doctor's bills for professional services in the 

 family circle, and there his responsibility 

 ended. Modern science has shaken this form 

 of indifference by demonstrating the pre- 

 ventability of most contagious and infectious 

 diseases. Epidemics have been studied enough 

 to convince the average man that their spread 

 in a normal, civilized community is nothing 



