Sept. 23, 1875J 



NATURE 



459 



of the purely meteorological question, and in the mean- 

 time place before the reader the conclusions of this 

 essay : — 



1. The idea of centripetal hurricanes of aspiration 

 originates in an illusion of the sense of sight ; it is an old 

 prejudice whose history it is easy to follow from the most 

 remote times to the present day. 



2. The theory of centripetal hurricanes, suggested by 

 this prejudice and the hypotheses which it implies, cannot 

 be accepted. The adoption of similar id -'as by enlightened 

 minds is only to be explained by the venerable authority 

 of this prejudice. 



3. Bases of the mechanical theory of gyratory move- 

 ments ; agreement of that theory with the Laws of 

 Storms. These ought to be considered as a first but 

 excellent approximation ; a means of making further 

 advances. 



I. History of a Nautical Prejudice. — In the midst of 

 the profound calm which often precedes thunderstorms, 

 the lower strata of the atmosphere are not agitated by the 

 least breath ; heavy clouds approach at a great speed and 

 cover the sky — a clear proof that powerful currents pre- 

 vail above, the influence of which does not extend to the 

 ground. From one of these clouds a sort of bag or end 

 of a tube or funnel is seen to issue, and which gradually 

 descends, lengthening at the same time. It seems to be 

 formed of the same material as the cloud ; and in fact 

 is a true fog which envelops the cloud, thus rendering it 

 visible to our eyes. 



Fig. s. 



Meantime the centre of this funnel is agitated by a 

 violent whirling movement of which the small whirlwinds 

 of dust that are sometimes seen on our roads give a very 

 accurate idea. When the waterspout reaches the ground 

 and encounters obstacles in its way, it sets to work upon 

 these after the manner of a turning machine of great 

 speed at the end of a vertical axis. It raises around its 

 lower extremity a cloud of dust, overturns trees, batters 

 down walls, and unroofs houses. If, instead of land, 

 the waterspout meets with a water surface, it acts upon it 

 like a square -bladed scoop at the end of a vertical axis, 

 and the churned water is thrown to a distance in foam ; if 

 it advances on a pool, is empties it in an instant ; if on a 

 lake or a sea, the water spurts out all round the foot of 

 the waterspout in clouds of spray. 



Look particularly at this long vaporous tube (Fig. 5), 

 which extends from the surface of the earth to the clouds, 

 to a height of from 1,600 to 2,000 feet and upwards ; it 

 appears flexible, and has an undulatory movement through 

 its entire length : the least breath of air alters and distorts 

 its form ; and its whirling movements are felt down even 

 to its base, which sweeps over the earth, carrying devas- 

 tation in its train. If it assumes greater dimensions, it is 

 no longer a waterspout, but a tornado. We have here in 

 two words the history of the tornado of Jan. 20, 1854, 

 which occurred in the county of Knox, Ohio, and which 



in half an hour levelled 50,000 trees with the ground, 

 hewing forjtself a pathway through the forest a quarter of 

 a mile broad, which could not have been made in some 

 weeks by a whole army of backwoodsmen. 



The tube, which takes the form of a pillar, a funnel, 

 the trunk of an elephant, &c., usually disappears after 

 being as it were broken across, by the violence of its 

 own gyratory movements. Further, the misty vapours 

 which compose it slowly ascend, and the combination of 

 the ascending and whirling motions gives the appearance, 

 when seen at some distance, of a spirally ascending move- 

 ment, which, however, bears no relation to the internal 

 gyrations of the waterspout. Movements, not real but 

 illusory, are all that are perceived. The spectator sup- 

 poses he sees objects ascending in the interior of the 

 waterspout. Thus a bit of cloudy vapour looks like a 

 bird caught by the waterspout and rapidly whirled aloft. 

 If the vermicular motion is continuous and along the 

 whole length of the waterspout, the question is asked, 

 what can in this manner ascend in a long tube whose 

 base is plunged into the sea and which violently agitates 

 its surface. At once and without any inquiry the logic of 

 the imagination comes into play, and the conclusion is 

 come to that it is the water of the sea which the water- 

 spout is in quest of ; this it pumps up and distributes 

 among the clouds, and its ascent up the tube is plainly 

 seen. No question is put as to how a tube composed of 

 aqueous vapour can hold and sustain deluges of solid 

 water. Moreover, are the clouds not seen rapidly to grow 

 portentously heavier and bigger by the water so abundantly 

 supplied by the waterspout ? 



It were idle to listen even to observations made under 

 such impressions. For thousands of years sailors have 

 transmitted from age to age tales of waterspouts which 

 have lifted ships into the air, sucked up the water of the 

 sea, and poured it down again on some hapless ship which 

 was unfortunate enough to pass under and break the tube 

 of the spout. Tales like these, unceasingly reproduced 

 with ever-fresh details, powerfully aid the illusion in deter- 

 mining the event before it is seen. 



{To be continued.) 



NOTES 



An interesting service to astronomy has been rendered by Mr. 

 Davidson, the head of the American Transit Expedition to 

 Nagasaki, Japan ; Jie has determined the exact site of Abbe 

 Chappe d'Auteroche's Observatory in 1769, when he observed 

 the transit by order of the French Academy of Science, at St. 

 Joseph, California. As Abbe Ciiappe died soon afterwards from 

 a fever caught while fulfilling his mission, his narration was 

 completed by people who had never been on the spot ; a blank 

 has been left'in thejecords of his observations, which has now 

 been filled up 108 years after the event. The Abbe Chappe was 

 an uncle of the celebrated Chappe who invented telegraphs 

 during the wars of the Revolution. 



M. Lecocq de BoiSBAUDRAN,'who is well known in connec- 

 tion with spectroscopic analysis, has just announced the dis- 

 covery, by means of the spectroscope, of a new cliemical element 

 which he calls gallium and affirms to be closely allied to zinc. 

 The spectroscopic character of gallium is two violet lines, one 

 corresponding to wave-length 417, and the other to 404, but 

 fainter. The communication was made by M. Wurtz, at 

 Monday's sitting of the French Academy. A commission has 

 been appointed to report on the discovery. Gallium is said to 

 be found in a special blende from Pierrefite mining works, in tlie 

 Argeles Valley. 



It appears that M. Janssen's observatory is to be built at 

 Fontenay at the expense of 80,000 francs. A sum of 50,000 francs 

 is to be spent on instruments, exclusive ot the apparatus used 

 in the transit of Venus, lie is to have two assistants, each of 



