894 



SCIENCE 



[N. S. Vol. XXVII. No. 701 



the relief (whether contouring, hachuring or 

 shading). 



A number of corollaries follow, a few of 

 which will be cited: 



Elimination of units too small for delinea- 

 tion should proceed by order of magnitude. 

 In a consistent map units of a certain order 

 should not appear in one place and be omitted 

 elsewhere. 



Elimination of units of one order should 

 not result in the enlargement of those of a 

 higher order. The delineation of the latter, 

 in order to be expressive, should so far as 

 possible suggest the presence and character of 

 the detail suppressed. 



Consecutive reductions in scale should carry 

 with them elimination of correspondingly 

 higher orders of units. 



In conclusion, it may be stated that the 

 practical application of these principles by the 

 topographer in the field proves to lead to no 

 revolutionary changes in mapping methods, 

 but on the contrary confirms the soundness of 

 the practise, intuitively established though it 

 may be, for the most part, of our ablest mod- 

 ern cartographers. 



Ealph Arnold, 



Secretary 



DISCUSSION AND CORRESPONDENCE 



GEOLOGICAL CLIMATES 



To THE Editor of Science: Dr. Lane, in 

 his interesting paper published in Science for 

 April 10, urges certain readers not to accept 

 my "ipse dixit" but rather to await further 

 promised demonstration. 



With the added evidence given in the last 

 issue of Science (pp. 784^5) it seems hardly 

 necessary to point out that, so far as theories 

 relating to terrestrial phenomena are con- 

 cerned, it now rests solely with the scientists 

 to demonstrate, if possible, that some vital 

 flaw exists in my published work; so long as 

 this can not be done, "most modern theories 

 of geological climate" must certainly be re- 

 garded as " upset," for these theories are hosed 

 upon an adopted value for the temperature of 

 space which is (according to my demonstra- 

 tion) too great hy nearly three hundred de- 

 grees of the centigrade scale at the earth's 



distance from the sun; and this result is prac- 

 tically independent of the errors of observa- 

 tion, for even if we should assume the meas- 

 ured focal temperature to be one thousand 

 degrees in error, the provisional value (1°.5) 

 for the temperature of space would be altered 

 only a degree or so. 



My result for the absolute temperature of 

 space is not a speculative one; until it is 

 proved incorrect it must stand as a demon- 

 strated fact which is in no way dependent on 

 other demonstrations to be given " later on." 



It may not be out of place to remark that 

 by attaching too much importance to the occa- 

 sionally unguarded assertions of great authori- 

 ties we are apt to retard, or to discourage, 

 original work along lines still demanding rigid 

 investigation. That a purely empirical for- 

 mula like Stefan's should, by common consent, 

 be honored to the extent of being called a 

 " law," is misleading ; that one of our great 

 living authorities should refer to " The estab- 

 lishment of Stefan's law " ' is still more mis- 

 leading. 



For myself, the most remarkable feature of 

 this whole controversy is the fact that it has 

 escaped the attention of scientists that, on 

 purely theoretical grounds, the results deduced 

 with the aid of Stefan's formula (or any other 

 formula except the Newtonian) can not be 

 in agreement with the principle of the con- 

 servation of energy. 



j. m. schaeberle 



Ann Aebor, Mich., 

 May 18, 1908 



" AMETHYSTINE BLUE." 



To THE Editor of Science : On page 825 

 of Science, May 22, 1908, Professor T. D. A. 

 Cockerell calls attention to the development 

 of the color of amethyst in glass exposed to 

 strong light, and also mentions that this color 

 is discharged by heat. 



I am writing this brief note to call atten- 

 tion to the fact that the phenomena mentioned 

 in Professor Cockerell's communication have 

 long been known to chemists, and the ex- 

 planation of same is very simple, viz., bottle 

 glass is usually made of cheap raw materials; 



> Science, March 27, p. 503. 



