National Academy of Sciences. 



13 



Is large, and the directions of the motions at tho surface 

 do uol differ much from those of the radii, and hence 

 there is au approximation to Espy's theory. As E<py 

 tok his observations mostly from tornadoes on laud, 

 and Redfleld took his mostly from large cyclones 

 at sea, each ono had observations which, with a little 

 bias in its favor, seemed to verity bis tlieory. Until re- 

 cently, no considerable number of observations have 

 been discussed to determine from observation the truth 

 of the preceding laws adduced from theory. Tuo Rov. 

 Clement Loy recently, from a great number of observa- 

 tions made by the signal service of England, France, 

 and Holland at 15 stations, has determined that the 

 average for tho angle between the direction 

 of motion and the isobar for all the stations 

 is nearly 21 degrees, and hence has verified the 

 theoretical law above. By taking the average, 

 also, for five stations on the coast, where the resist- 

 ances, siuce part of the gyration is on the sea, are less* 

 he found the value of this angle only 13, while for 

 five other stations entirely inland, where the resistances 

 are greater, the average gave 29 D fur the value of this 

 angle. This verifies another part of the theory above, 

 naujely, that the greater the resistances the more must 

 the directions of motion deviate from that of the isobar, 

 and consequently the more must the gyrations deviate 

 from the circular gyrations of Reclfield's theory. 



When Mr. Ley considered the observations separately 

 from the different quarters from which the wind blew, 

 he obtained for the angle of deviation from the isobar' 

 61 decrees on the N. E. side of the cyclone, 18 degrees on 

 the west side, 9 degrees on the S. W. side, and 20 degrees 

 on the S. E. side. He also states that the average direc- 

 tions in which the cyclones move is toward the N. i,. 

 Hence the angle between tho direction of motion and 

 the isobar for the front part of the cvclone seems to be 

 much greater than that for the rear. For this no very 

 plausible reason is apparent, but several probable ex- 

 planations might bo given. 



It is commonly supposed that the gyrations of a cy- 

 clone in all parts are the same way, that is, from right 

 to left in the northern hemisphere, and the contrary in 

 the southern hemisphere; but this is not the case. In 

 every cyclone in the northern hemisphere the gyrations 

 are from right to left in the interior part, while th?y are 

 from lefc to right in the external part, but the gj'rations 

 in the interior are much the more rapid, the motions of 

 the exterior gyrations amounting usually to only gentle 

 winds. Tue highest barometric pressure is ou the 

 dividing line between the two systems of gyrations. 



As the motion toward the center in the lower part of 

 the cyclone causes the direction of the wind to 

 deviate from the isol-ar on the side toward the 

 center, so the outward motion in the upper part of the 

 cyclone must cause the direction of tho wind to deviate 

 on the side from the center, and there must bo a certain 

 median plane where there is no motion either toward 

 or from the center, and where the direction of 

 the wind must coincide with that of the isobar, that is, 

 where the gyrations are entirely circular. If, therefore, 

 an observer stands with his face exactly toward tho 

 wind below, tho clouds in the upper strata, moving 

 with the directions of the wind there, must always come 

 from a direction a little to the right of the observer, and 

 the lusher the clouds in general, tho greater muse be the 

 difference in the directions. 



Beside the ordinary cyclone of which we have treated, 

 there is also what is called an anti-cyclone. In this 

 kind of cyclone the denser and heavier part of the at- 

 mosphere is in tho center, and hence the air descends 



thero and flows out on all sides below, and In from all 

 sides above, and hence the motions in a vertical piano 

 are just the reverse of those of an ordinary cyclone. 

 For this reason it U generally supposed that the hori- 

 zontal gyrations are also reversed in an anti-eyelone; 

 but this is a mistake 1 . T.ie gyrations in both cyclones 

 are precisely the same, and such as have l>e>-ii give.i for 

 tho ordinary cyclone. Anti-cyclones aiv ;ilways station- 

 ary; having their centers lu tho interior of a continent 

 or larger island where the atmosphere in Winter is 

 colder and consequently heavier than over the sur- 

 rounding sea; and hencs it descends in the middle and 

 flows out at all sides below, aud tho deflecting force 

 already explained gives rise to a stationary cyclone. 



Each hemisphere of the earth contains one grand anti- 

 cyclone, with the cold Polo in the center and the one- 

 half of the torrid zone for its external warmer part, 

 and in these anti-cyclones we have a verification of what 

 is stated above, since in the northern hemisphere tho 

 gyrations nearest the Pole are from right to left, giving 

 rise to the eastward current in tho mid'llo aud higher 

 latitudes, while toward the external border at tho 

 equator the gyrations are the contrary way, giving ri-o 

 to the general westward motion of the air in the torrid 

 zone. lu this case, also, as in ordinary cyclones, the 

 barometer stands the highest at the dividing paraliol of 

 latitude of about 35 degrees, which separates the two 

 systems of gyrations or winds. 



At the business session, Prof. F. A. P. Barnard, 

 President of Columbia College, New- York, was 

 elected Foreign Secretary, vice Prof. Agaseiz, de- 

 ceased. The constitution and rules limit the num- 

 ber of members to be elected annually to five. The 

 following individuals were honored by election 

 April 23: Prof. C. F. Chandler of New- York, chem- 

 ist ; Geo. Davidson of San Francisco, mathematician 

 and astronomer; Prof. 0. C. Marsh of New-Baven, 

 Conn., geologist; George W. Hill of Nyack, N. Y., 

 mathematician ; Prof. Henry Morton of the Stevens 

 Institute, lioboken, N. J., physicist. 



LAST DAY OF THE MEETING HASTE 

 THE SAKE OF ADJOUKN.MKXT. 



SCIENTIFIC VALUE OF THE POLARIS VOYAGE AN IN- 

 TERESTING DEBATE ON THE FORMATION OF THE 

 NORTHERN PART OF THE CONTINENT THE GREAT 

 TELESCOPE A GREAT SUCCESS OTHER SATELLITES 

 LIKE OUR MOON LAWS OF STORMS SILURIAN 



FOSSILS. 



WASHINGTON, April 24. It was evident when the 

 session of the day began, that the Secretary, Prof. 

 J. E. Hilgard, was pushing matters with unusual 

 rapidity. There were many papers of interest and 

 value that had been under consideration, which 

 were either declined, read by title (that is, not read 

 at all, except the title) or hurried through with little 

 ceremony. Two or three times a rising debate on 

 tho subjects presented was brought to a close by an 

 appeal from the Secretary urging baste. And, to tho 

 surprise of most of the members and all of the audi- 

 dience. the Academy did actually Irnish its pro- 

 ceedings and finally adjourn at the usual hour of 

 closing the session for the dnv. 



If those who imagine that the work of Polar expe- 

 ditious is a mere useless expenditure of enthusiasm 



