August -ii, il 



SCIENCE. 



99 



ciahle influence upon the deflection of the magnel-needle, even 

 thougli the velocity of the current were very large as compared 

 with that of the conductor. In order to render the detection of 

 this presumably very small effect less difficult, the direct influence 

 of the coil was eliminated by differential winding. Under these 

 circumstances, when the coil was carrying as large a current as it 

 could be made to do without injurious heating, the rotation of the 

 coil was found to be without appreciable effect upon the magnetic 

 moment of the same. The best results were obtained by sending 

 4.6 amperes of alternating current of 40,000 alternations per minute 

 through the coil. 



At a velocity of the wire equal to S.ooo centimetres per second, 

 they produced no effect upon the needle amounting to 0.2 milli- 

 metre deflection. The figure of merit of the coil and needle was 

 determined by substituting a coil of continuous winding, its posi- 

 tion with respect to the needle being the same as that of the rotat- 

 ing coil, and determining the current necessary to produce one 

 centimetre deflection. The sensitiveness of the apparatus was 

 found to be such that a current having direction and a velocity of 

 1,000.000,000 metres per second would have shown a change in its 

 action upon the needle (when the motion of the coil was 380 revo- 

 lutions. S,ooo centimetres per second) amounting to o.i centi- 

 metre deflection, — an effect which could not have escaped obser- 

 vation. It follows from the above negative result, that, if the electric 

 current consists in the flow of a inedium or fluid through the con- 

 ductor, the velocity of the same must be greater than the exceed- 

 ingly high rate just mentioned. Fopl, who in some recent experi- 

 ments used an apparatus in most essential particulars similar to 

 their own, but one by means of which only relatively very low 

 velocities could have been detected, has reached the same negative 

 conclusion. 



Monday was almost exclusively devoted to electrical inatters, 

 while only few papers on the subject were read on the preceding 

 days. While the interest of the section was concentrated in theo- 

 retical questions, a few problems of practical import were discussed. 

 A new form of electro-magnetic telephone was described by R. B. 

 Fulton, and the efficiency of incandescent lamps was treated by E. 

 Merritt. Messrs. E. L. Nichols and W. S. Franklin gave the inter- 

 esting results of their spectro-photometric comparison of sources of 

 artificial illumination, which have an eminently practical bearing. 

 C. J. H. Woodbury discussed the protection of watches against 

 magnetism, — a problem that has become of importance since the 

 increased use of electricity for industrial purposes. 



The programme of the Mathematical Section embraced many 

 problems of geophysics and astronomy, as well as discussions on 

 the theory of physical instruments. Among twenty-one papers 

 read, six were purely mathematical, while the greater number of 

 the rest referred to astronomy. One of the most interesting of the 

 latter class was Prof. A. Hall's paper on ' The Appearance of Mars 

 in June, 1S8S.' It will be remembered that recently remarkable 

 changes in its surface were'observed which it is difficult to account 

 for. Professor Hall has recently paid considerable attention to this 

 subject, and has observed the planet on eighteen nights, from June 

 I to July 2 inclusive. 



While observing satellites in April, attempts were made on sev- 

 eral nights to see the canals of Mars, but without success ; and Pro- 

 fessor Hall determined to make the trial in twilight, when he had 

 been able to see more detail on the surface of planets. However, 

 he was not able to see any thing like the regular canals drawn by 

 European observers, although the usual reddish and dark spots and 

 markings were visible nearly every night. The only remarkable 

 change which he noticed during June was the diminution in the 

 size of the white spot at the south pole of the planet. On June i 

 the spots at the poles were a good deal extended, but on July 2 

 the one at the south pole had become very small and round. 



The color and brightness of the sky, and the methods of exact 

 measurements, were treated in the Mathematical and Physical 

 Sections. While in the latter Prof. F. P. Whitman reported on 

 certain photographic experiments, in the former Henry M. Parkhurst 

 of New York City read a paper upon ' The Effect of the Brightness of 

 the Sky in extinguishing the Light of Stars ' with special reference 

 to photometric observations with a wedge of neutral-tint glass. The 

 presence of moonlight, of twilight, and even of ordinary starlight. 



diminishes the effect of the wedge according to the aperture of the 

 telescope and the magnifying-power employed. By observations 

 during the day he had ascertained that the effect of the wedge in 

 extinguishing stars was reduced to less than one-tenth what it was 

 in the evening. He also presented formul.x- by which the effective 

 value of the wedge can be ascertained under different degrees of 

 illumination. 



In the Chemical Section a report of the committee on water- 

 analysis was read, from which we learn, that, so far, the proposi- 

 tions of the committee have not met with much encouragement in 

 England. The question of water and water-supply was treated by 

 Albert W. Smith with special reference to Cleveland and the water 

 of Lake Erie, while E. H. S. Bailey spoke on the significance of the 

 presence of ammonia in water. Prof. Frank H. Morgan of Cornell 

 University also discussed the progress in chemical methods of 

 water-analysis, and gave a preliminary notice upon iodine as a re- 

 agent in the analysis of drinking-water. The last day of the meet- 

 ing was devoted to the presentation and discus.sion of laboratory 

 methods. 



On account of the absence of the vice-president. Prof. C. M. 

 Woodward of St. Louis. Section D (Mechanical Science) did not 

 organize until the second day of the meeting, and work was not 

 begun until the third day. Lieutenant Peary's paper, on ' -Surveys 

 for the Nicaragua Canal,' is mentioned below. In connection 

 with this may be mentioned W. Nelson's paper on ' The Panama 

 Canal,' which was illustrated by stereopticon views. As these 

 subjects are pretty well kept before the eyes of the public, we re- 

 frain from a detailed report on the papers. 



Considerable interest was excited by W. J. Keep's, C. F. 

 Mabery's, and L. D. Vorce's statement on the influence of alumin- 

 ium upon cast iron, in which it was shown that the addition of 

 aluminium materially increases the strength of iron, that it causes 

 the carbon to be changed from the combined to the graphitic state, 

 and secures many other advantages. 



If we turn to the proceedings of Section E (Geology and Geog- 

 raphy, or, more properly Geology, as no geographical papers were 

 read), we find ourselves somewhat embarrassed by the great num- 

 ber of valuable papers that were presented, and by the important 

 facts and theories contained in many of them. We can therefore do 

 no more than point out a few of the most important features of 

 these lectures. Geologists from numerous States were present ; 

 but, Cleveland being situated on the Great Lakes, the theory of 

 their origin and the glacial period in general chiefly attracted the 

 attention of the meeting. This was principally the case on Friday, 

 when J. W. Spencer read his interesting series of papers on ' Lake 

 Warren and its Later History.' 



Lake Warren is the first chapter in the histor)' of the Great 

 Lakes, and is subsequent to the deposit of the upper bowlder clay, 

 and therefore the lakes are all very new in point of geological time. 

 By the movements of the warpings of the earth's crust, as shown 

 in the beaches, — after the deposit of the later bowlder clay, — the 

 lake region was reduced to sea-level, and there were no Canadian 

 highlands northward of the Great Lakes. Upon the subsequent 

 elevations of the continent, beaches were made around the rising 

 islands. With the rising of the land, barriers were brought up 

 about this lake region, producing Lake Warren, — a name given to 

 the sheet of water covering the basin of all the Great Lakes. A 

 succession of beaches of this lake have been partially worked out 

 in Canada, Michigan, Ohio, Pennsylvania, and New York, covering 

 almost thousands of miles. Everywhere the differential uplift has 

 increased from almost zero about the western end of the Erie basin, 

 to three, five, and in the higher beaches to from five to nine, feet 

 per mile. With the successive elevations of the land, this lake be- 

 came dismembered, and the present lakes had their birth. The 

 idea that these beaches in Ohio and Michigan were held in by 

 glacial dams to the northward is disproven by the occurrence of 

 open water and beaches to the north, which belong to the same 

 series, and by the fact that outlets existed where placid dams are 

 required. 



■VVith the continental rise described above, owing to the land 

 rising more rapidly to the north-east. Lake Warren became dis- 

 membered, and Huron, Michigan, and Superior formed one lake ; 

 the Erie reallv was lifted out of the bed of Lake Warren, and be- 



