188:}.] 



SCIENCE. 



621 



cloud above, almost as soon as formed, the condi- 

 tions necessary to its full development not existing. 



In his excellent article on tornadoes, in the current 

 number of the Kansas City revirw of science, Mr. 

 John D. Parker speaks of the four characteristic 

 motions of those meteors. These motions might be 

 classified as horizontal and vertical. The horizontal 

 motions are the linear, caused by the forw.ard motion 

 of the air-current governing tlie direction of the 

 storm-cloud ; second, the gyratory motion, caused, 

 as above stated, by the mutual resistance of air- 

 currents moving in different directions; third, the 

 swaying motion, due partly to the varying pressure 

 on different sides of the tunnel, and partly to the 

 %'ertical or bounding motion of the tunnel. This 

 latter motion would not have a very marked effect in 

 producing the ' dentated edges ' of the storm's path, 

 if the tunnel-cloud were vertical instead of slanting. 

 What causes the bouiuling motion it is difficult to 

 say, but it certainly resembles electrical attraction 

 and repulsion. This bounding movement was very 

 marked in the tornado of .\pril IS, 1809, which passed 

 near this locality: but occurring, as it did, in the day- 

 time. 1 could not distinguish the illumination of the 

 lower part of the tunnel, which may sometimes be 

 seen wlien these storms occur after dark, and which 

 some think is due to electricity. 



It is interesting to produce in miniature the hori- 

 zontal motions of the tornado by the following 

 simple experiment. When there is a good fire, let a 

 small quantity of liglit, flaky ashes, or other light 

 material, be sprinkled over the whole top of the cook- 

 ing-stove. Tlie heat forms quite a strong current, 

 ascending mainly from the central parts toward the 

 pipe. Cool currents flow in from all sides. Now, 

 with the hand or a fan, produce local or opposing 

 currents over the luxated surface, and at once little 

 tornadoes are developed, whirling the ashes several 

 inches in the air. I have often produced them on 

 both sides of the stove at the same time; those on 

 the left moving as tornadoes in our latitude, and 

 those on the right in the opposite direction. Now, 

 are not the causes of the gyratory motion of the little 

 whirlwinds on the stove, tiny as they are, the same 

 in kind as those which produced the storms which 

 devastated Marshtield, Grinncll, or Cam.anche? If 

 this be answered in tlu; affirmative, the rotation of 

 the earth plays no direct part in causing the gyratory 

 movement of this class of storms. Of course, the 

 rotation of the earth causes the higher currents of 

 air to move toward the north-east, instead of due 

 north, as they pass from the equatorial to the arctic 

 zone, and these currents determine the general linear 

 movement of storms in our latitude: but this makes 

 it proper to consider the gyratory motion an indirect 

 result rather than a direct consequence. 



S. A. Maxwei.i,. 

 Morrison, III., Oct. «, 1S83. 



The chinch-bug in New York. 

 Why should Mr. Linlner conclude that the chinch- 

 bug was brought to St. Lawrence county, N.Y., in a 

 freight-car from the west? Harris corrects the erro- 

 neous idea that it is confined to the states south of 

 40° of latitude by demonstrating its occurrence in 

 Illinois and Wisconsin, while Fitch's record of find- 

 ing it in northern New York would justify us in 

 assuming that it has always existed there, especially 

 when we know that its range is much farther north. 

 Packard found it on the top of the White Mountains; 

 and it is to-<lay the most serious enemy that Ihrealeus 

 the vast wheat-fields of Dakota. It seems to me 

 more rational to consider this injurious manifestation 



in Ni'W York a result of undue increase of a species 

 always there than to call it an invasion. Though we 

 rarely hear of its injury in the Atlantic states, yet it 

 is commonly met with where collecting is done near 

 or in the ground, and in dry years is by far the most 

 common Ileleropter in grain and grass fields and 

 dunes. This 1 know from |)ersonal experience, and 

 have found it as far nortli as Koscawen, N.ll. 



Should it prove less susceptible to lieavy and con- 

 tinued rains in New York than elsewhere, the fact 

 will be remarkable. Such rains affect it most, how- 

 ever, in spring and early summer. My own inter- 

 pretation of the interesting facts recorded by Mr. 

 I.intner would be, that the .species multiplied exceed- 

 ingly during the very dry seasons of 1880 and 18S1, 

 and that the wet season, which it has so far braved 

 (as it often does for a while in the west), will never- 

 theless tell on the hibernating bugs. In this view 

 there Is cause for encouragement rather than alarm. 

 A careful survey would undoubtedly show, as Mr. 

 Lintner suggests, that it exists in many places in the 

 state where it has not vet been detected. 



• ■ C. V. Riley. 



AVashington, D.C, Oct. 24, 1883. 



Unusual reversal of lines in the summit of a 

 solar prominence. 



On Oct. 17, between :5.4.") and 4.30, local time 

 (about 8.-15 and '.KoO Greenwich time), a rather unu- 

 sual phenomenon was observed at Princeton, in a 

 prominence connected with the large and active 

 group of spots which at that time was just passing off 

 from the sun's disk. 



The prominence had the very common form of a 

 number of overlapping arches, with a sort of cap 

 above them, or of a cloud connected bysever.al curved 

 stems to the chromosphere below. Its elevation was 

 about 2', and its extent along the sun's circumference 

 a little less. 



The peculiar features were the extreme brilliance of 

 the cloud-cap at the summit of the prominence, and 

 the perfect delineation of tlie fonu of this cloud in 

 certain spectrum-lines, which ordinarily are reversed 

 only at the base of the chromosphere; while, at the 

 same time, certain other lines, which not unfrequently 

 are reversed at considerable elevations, showed its 

 form only very faintly, or not at all. 



When I first came upon the prominence, in run- 

 ning around the sun's limb with the spectroscope, 

 the brightness of the cloud-cap, as seen through the 

 C line, was simply dazzling. I do not remember ever 

 to have seen a prominence, or any part of one, quite 

 so brilliant. At the same lime, the line X 0076.9 

 (which is in the same field of view with V, .and is 

 No. 2 of my catalogue of chromosphere-lines, — a line 

 attributed to iron f also showed the top of the cloud 

 quite as well and as brightly as is usual in C under 

 ordinary circumstances. The chromosphere, also, was 

 faintly visible in the same line; but the stems and 

 lower portion of the cloud could not be seen at all in 

 it. On turning to line X7U.'J5 (No. 1 of tlje catalogue), 

 I was suiprised and gratified to find the same appear- 

 ances conspicuous in this line also. A careful search 

 failed to show any other lines reversed below C. 



liunning up the spectrum from (J to D, I could not 

 find any lines showing the top of the prominence, 

 though a considerable number were reversed in the 

 chromosphere at its base. D,, of course, showed 

 the cloud-cap magnificently, but /), and D^ only 

 very faintly, though dislinctli/ enough. 



Between X> and b the same remarks apply as be- 

 tween Cand J). Thecorona-line,A5315.9, was reversed 

 at the base of the prominence a little more brightly 



