812 



SCIENCE 



[N. S. Vol. XXVII. No. ( 



of enjoying these things, I say, as fiction. 

 Imaginative advertising, as advertising, 

 has delighted me from the start. I have 

 re^d them all from "Sunny Jim" to the 

 ' ' Gold Dust Twins. ' ' But, after all, could 

 we not purchase more intelligently if we 

 were better posted on composition and less 

 on catch-phrases and cartoons? Is it too 

 much to hope that chemical composition 

 will one day be the public's guide in 

 matters of this sort? Carnation milk, 

 Violet wafers. Butternut bread. Bullfrog 

 beer, Buttermilk soap and Grapenuts! I 

 can see an opportunity for chemistry here ! 

 In conclusion, there may be some present 

 who will think I have praised chemistry 

 and chemists too highly. Some may say 

 that important matters speak for them- 

 selves and need no praising. I am not in 

 the least of the opinion that chemistry 

 needs praising; what it does require in 

 this country is, calling the public's atten- 

 tion to its importance. 



W. D. ElCHARDSON 



SOME RESULTS OF TEE MAGNETIC 8UR- 

 TET OF THE UNITED STATES '' 



The United States of North America, 

 embracing nearly one fifteenth of the 

 entire land area of the globe, or an area 

 about equal to that of Europe, constitutes 

 at present the largest land area for which 

 a general magnetic survey, in sufficient de- 

 tail and of the requisite accuracy, has been 

 made. The three magnetic elements: the 

 magnetic? declination, the inclination and 

 the intensity of the magnetic force, have 

 been determined at about 3,500 fairly uni- 

 formly distributed points. Of this number 

 of stations about two thirds were occupied 

 during the seven yeare the speaker had 

 charge of the magnetic operations of the 

 United States Coast and Geodetic Survey, 

 viz., 1899-1906. 



" Presented before the National Academy of Sci- 

 ences, Washington, D. C, April 22, 1908. 



The stations are, on the average, thirty 

 to forty miles apart, or we may say there 

 is, on the average, one station for every 900 

 or 1,000 square miles. Of course, in some 

 states, e. g., in the coast states, the distribu- 

 tion of stations is somewhat denser than ta 

 some of the interior western states, because 

 the early magnetic work of the Coast 

 Survey was largely confined to the Atlantic 

 and Pacific coasts. However, before many 

 years the distribution for aU the states 

 will be practically the same. When this 

 has been accomplished, the plan is to 

 multiply stations in the regions of manifest 

 irregularities. (Two slides were exhibited, 

 one showing the distribution of the stations 

 up to 1899 and the other up to January 1, 

 1907.) 



Because of this large amount of accurate 

 magnetic data now available for the United 

 States, I was enabled to construct the mag- 

 netic maps of the United States, for the 

 first time as based iipon strictly reliable 

 and homogeneous data. My predecessor, 

 the late Charles A. Schott, who had been a 

 member of this academy, was obliged to 

 base his isogonie maps or "lines of equal 

 magnetic declination" very largely upon 

 surveyors' data, owing to the paucity of 

 data, whereas his isoclinie and isodynamic 

 maps had to rest upon even more slender 

 material. In the present instance, how- 

 ever, the charts of the various magnetic 

 elements all depend upon practically the 

 same number of observations made at the 

 same points. They are, hence, strictly 

 comparable and we may, therefore, pursue 

 our investigations respecting the irregu- 

 larities in magnetic distribution much 

 more successfully than hitherto. 



Mention should also be made that dur- 

 ing the period 1899-1906 special atten- 

 tion was paid to instrumental errors — 

 more frequently inherent in magnetic in- 

 struments than generally supposed. AU 

 instruments were therefore studied care- 



