62 



SCIENCE 



[N. S. Vol. LII. No. 1333 



hundred pages, clearly printed on good paper, 

 and substantially bound in convenient format. 

 The experience of a veteran text-book maker 

 and user shows in every feature of this book's 

 construction. 



The new book is " affectionately inscribed " 

 to the author's "old students whose youthful 

 enthusiasm was a constant inspiration " dur- 

 ing a long period of service as teacher, as an 

 effort to further aid them, though they are now 

 gone from his classrooms and laboratories. 

 Professor Comstock may rest assured that his 

 greeting will be quite as affectionately re- 

 turned, and that his latest effort will be as 

 gratefully received by his many scattered stu- 

 dents, mostly now no longer youthful, as were 

 his earlier efforts to instil in them that love 

 of nature and passionate interest in learning to 

 know nature's works which have been for so 

 many years beautifully characteristic of their 

 beloved mentor. These old students will be 

 greatly helped by this effort in their attempts 

 to carry on to new students the Comstock tra- 

 dition. And American entomology has not 

 had, nor will ever have, any finer tradition. 

 Vernon Kellogg 



SPECIAL ARTICLES 



" PHYSICAL CONSTANTS " PERTAINING TO 

 THE OCEAN 



An important object of the science of 

 physics is deecription of the behavior of 

 different substances. Expression in mathe- 

 matical form of such descriptions requires 

 the use of one or more " physical constants," 

 such as the coefficient of elasticity, conduc- 

 tivity, etc. Constants thus obtained are gen- 

 erally regarded as intrinsic, or peculiar to 

 the substance. The extensive list of " phys- 

 ical constants " already determined bears wil^ 

 ness to the achievements of physics, and con- 

 stitutes fundamental quantitative data of the 

 science. 



Application of the methods of physics to 

 terrestrial phenomena taking place on a cor- 

 respondingly immense scale, has likewise re- 

 sulted in physical laws or descriptions capable 

 of expression in mathematical form. But 

 the corresponding " physical constants " can 



not be evaluated by means of experiments 

 necessarily limited to much smaller dimen- 

 sions. The influence of the enormous magni- 

 tudes involved in many terrestrial phenomena 

 can be determined only by observing the phe- 

 nomena as they take place in nature. It is 

 impossible, for example, to determine in de- 

 tail the motion of the water particles in the 

 convective circulation of even a limited part 

 of the sea. But this would be necessary in 

 order to resolve the water mass into suffi- 

 ciently small portions to justify the assimap- 

 tion, made in laboratory experiments, of flow 

 in plane layers. Even if this resolution of 

 the complex motion into its elements were 

 possible, there would still be the impracticable 

 task of summing up the effects of the corre- 

 spondingly complex and irregular system of 

 forces in order to obtain the resultant effect. 

 The only recourse is to observe the system as 

 a whole imder the actual conditions of the 

 sea. For example, a decade ago, the Swedish 

 physicist, V. W. Ekman, applied the classical 

 hydrodynamical equations to certain ocean 

 current observations, but replaced the viscos- 

 ity coefficient by a constant representing the 

 integrated effect of the complex system of 

 frictional forces. The value of this constant 

 is thousands of times greater than the coefS> 

 cient of viscosity of sea-water. A generation 

 ago, a German mathematician, Zoppritz, de- 

 veloped an elaborate mathematical theory of 

 ocean currents, but used laboratory values of 

 the physical constants. Consequently his 

 theory disagreed widely with subsequent ob- 

 jective knowledge. Such residts emphasize 

 the fact that physical constants are depend- 

 ent not only upon the nature of the sub- 

 stances, but also upon the corresponding ex- 

 ternal conditions, and must therefore be 

 determined under the conditions prevailing 

 where they are to be used. 



Progress in laboratory investigations is 

 continually demonstrating the variability of 

 quantities originally regarded as physical 

 constants. Further refinement often requires 

 the substitution of a variable, dei)endent upon 

 additional conditions, for constant quantities 

 of earlier formulse. This is also true in 



