26 ASSOCIATIONS FOR THE ADVANCEMENT OP SCIENCE. (AMERICAN.) 



serration that existing offshore deposits are 

 coarse at the top, shading down to fine by the 

 same law as that marked in the structure of 

 mountains. But the enormous mountainous de- 

 posits would have been possible only where there 

 was a corresponding subsidence of sea bottom. 

 The earth sinks by loading, and rises by unload- 

 ing. Of this the Colorado plateau furnishes an 

 illustration. It was originally 20,000 feet high, 

 but 12,000 feet have been removed by erosion, 

 which has caused the remaining 8,000 feet to 

 rise above the general level. It may be regarded 

 as now proved that the cosmic behavior of the 

 earth is that of a rigid solid. A solid globe of 

 glass six feet in diameter will change shape by 

 the pressure of its own weight. The earth does 

 the same. But as the earth is not homogeneous, 

 its radial contraction will be unequal, and hence 

 there will be ridges. The contraction theory as- 

 sumes that the earth was once an incandescent 

 ball, now cooling ; and this cooling compels 

 yielding along its lines of weakness. This is 

 known abroad as the " American theory," and 

 was originated by Prof. Le Conte. He also out- 

 lined other theories of mountain origin, and 

 pointed out their defects, declaring, however, his 

 entire willingness to give up his theory whenever 

 any better one had been presented. 



Proceedings of the Sections. The associa- 

 tion is divided into eight sections, each of which 

 is presided over by an officer having the rank of 

 vice-president of the association. Subsequent to 

 the opening proceedings each section meets by 

 itself and effects its organization by electing a 

 fellow to represent it in the council, a sectional 

 committee of three fellows, a fellow or mem- 

 ber to the nominating committee, and a com- 

 mittee of three members or fellows to nomi- 

 nate officers of the section for the next meeting. 

 As soon as this organization is effected the secre- 

 tary of the section reports to the general secre- 

 tary, who then provides him with a list of papers 

 that, having been considered suitable by the 

 council, may be read and discussed before the 

 section. On the first day the proceedings are 

 usually confined to organization and the delivery 

 of the inaugural or vice-presidential address. 



Sections. A. Mathematics and Astronomy. 

 This section was presided over by Charles L. 

 Doolittle, of South Bethlehem, Pa., who chose as 

 the subject of his address " Variations of Lati- 

 tude." He said : " ' All astronomy,' says Laplace, 

 ' depends upon the invariability of the earth's 

 axis of rotation upon the terrestrial spheroid and 

 upon the uniformity of their rotation.' He adds 

 that, ' since the epoch when the application of 

 the telescope to astronomical instruments gave 

 the means of observing terrestrial latitudes with 

 precision, no variations in such latitudes have 

 been found which could not be attributed to er- 

 rors of observation ; which proves that since this 

 epoch the axis of rotation has remained very 

 near the same point on the terrestrial surface.' 

 The question still persists whether it represents 

 more than a first approximation to the truth. 

 Various authorities were cited to show the cor- 

 rectness of this view ; but as the geological evi- 

 dence is clear that at one time the poles were 

 temperate and the temperate zone a field of ice, 

 the question is still an open one. A very plausi- 

 ble explanation of these things is by the assump- 



tion that the earth's axis had in times past wan- 

 dered from its former place. Hence the problem 

 that the practical astronomer is asked to solve 

 is that of determining whether progressive 

 changes in the position of the pole are now tak- 

 ing place. Concerning these the most logical 

 course at present is to suspend judgment. With 

 regard to periodic changes, on the other hand, we 

 can speak with more confidence. Considerable 

 progress has been made in the investigations 

 along this line, chiefly by such authorities as 

 Kiistner, Newcomb, and Chandler. The latter 

 especially has made notable contributions in his 

 valuable papers printed in the ' Astronomical 

 Journal.' These and other researches which were 

 discussed clearly demonstrate the fact of specific 

 periodic variations of latitude. For further 

 improvement in our knowledge of this subject 

 we must look to continued observations at a 

 number of points carried on for this express pur- 

 pose, and so conducted as to eliminate all sys- 

 tematic errors. A plan is under consideration 

 for establishing four permanent latitude stations 

 on the same parallel of latitude at intervals of 

 90 degrees in longitude as nearly as may be. 

 These will presumably be equipped with iden- 

 tical instruments of the most approved form, and 

 the same stars employed at all of them. It is 

 possible that within a very few years we shall 

 see some such system in full and successful opera- 

 tion." The following-named papers were read 

 and discussed before the section : 



"A Construction for the Imaginary Points and 

 Branches of Algebraic Loci," by Frank II. Loud ; 

 " Upon the Latitude Variation Tide," by Alexander 

 S. Christie ; " The Screw as a Unit in a Grassmannian 

 System of the Sixth Order," by Edward W. Hyde ; 

 " Latitude Determination at Bethlehem, 1892-'93," 

 by Charles L. Doolittle ; " A Determination of the 

 Constant of Aberration by a Modified Form of the 

 Loewy Method," by George C. Comstock ; " Applica- 

 tions of the Generalized Logarithmic Theorem," by 

 Alexander Macfarlane ; " On the Inscription of Reg- 

 ular Polygons," by L. E. Dickson ; " On the Possi- 

 bility of the Algebraic Solution of the Gen-equation 

 of the Fifth Degree," by Mansfield Merriman ; and 

 " Space," by Samuel S. Laws. 



B. Physics. The presiding officer of this sec- 

 tion was Prof. Edward L. Nichols, who holds the 

 chair of Physics in Cornell University, Ithaca. 

 The topic which he discussed was " The Phe- 

 nomena of the Time Infinitesimal." 



Prof. Nichols pointed out the importance in 

 physics of the study of phenomena occupying 

 short intervals of time, particularly of the first 

 minute intervals following abrupt changes of the 

 conditions of equilibrium, and also of the suc- 

 cessive time elements, which go to make up a 

 cycle in the case of periodic changes. He re- 

 viewed at some length the most significant re- 

 searches already completed in the field, and 

 traced in detail the development of the " method 

 of instantaneous contacts," which has been so 

 fruitful in the experimental study of alternating 

 current phenomena, claiming that their complex- 

 ity had obliged the modern electrician to be 

 both a mathematician and a physicist. In much 

 the same way a generation ago the new and diffi- 

 cult phenomena of cable telegraphy served to 

 train the men who stand as pioneers and chief- 

 tains in electrical science. The special adapta- 

 bility of photography to the investigation of 



