312 



NATURE 



[Feb. 8, 1877 



helix, and therefore if the water be driven in at the large end 

 and up to the small end of the spiral, it should considerably in- 

 crease in height as it went along and move with greater rapidity. 

 When arrived at the extremity of the spiral, it may be con- 

 sidered to remain there for some time and spread itself out 

 laterally in bulk at the high level as long as the violence of the 

 storm ^lasted. But when the force of the wind began to diminish, 

 this helped aqueous mass would more or less suddenly subside, 



Cyclone — Horizontal Plan, 



and rush down on all sides to seek its natural level. This 

 might occur at sea, and be evidenced by the long swell or rollers 

 frequently seen, or might be translated by progressive motion 

 to launch its tremendous weight on the land, and inundate it. 

 This, it may be conjectured, could only be effected over lands 

 about the level of the sea, over which the base of the funnel of 

 the cyclone would advance, carrying the inclosed mass of water 

 with it for part of the area of the revolving circle, which would 

 so far be still able to draw its supplies from the sea on the 

 coast yet included in its motion. As soon, however, as the 

 southern or equatorial limb of the circle had so far progressed as 

 to leave the sea behind it, then the friction of the earth would 

 prevent the inclosed mass of water following the cyclone, which 

 had been already cut off from its aqueous communication, and it 

 would be left behind to expand over and deluge the country lying 

 under its level. 



In speculating on the dimensions of the Bengal storm-wave we 

 may assume, from the statements in the newspapers, that it was 

 a disc of fifty miles in diameter and twenty feet deep, when viewed 



The means for counteracting the disastrous effects of the storm 

 or cyclone-wave in the Delta of the Ganges on life and property, 

 would probably be found in the erection of mounds, as proposed 

 by a writer in the Times. As this tract of country would be 

 destitute of stone or rock, and be composed chiefly of mud and 

 sand, it would be requisite to convert this into bricks first, as the 

 mud-mounds would not stand the impact of the storm- waves, 

 even in this country. 



The design for the construction of these mounds would pro- 

 bably be most suitable after the model of the celebrated Tower 

 of Babel, projected by the post-Diluvial inhabitants of Mesopo- 

 tamia for a like purpose of self-preservation from inundation. 



Vortex 



"Polar Cyclones" — Etna Observatory 



In reply to Mr. Clement Ley's letter in Nature, vol. xv. 

 p. 253, I fear I cannot at all agree with him as to the cause of 

 the polar depressions of the barometer. He says : " The ' polar 

 cyclones ' appear to be themselves aggregates of those local de- 

 pressions, or cyclones, which have penetrated into the Arctic or 

 Antarctic regions, and have there partially or wholly coalesced." 

 Now, let us test the question in this way : — Suppose the surface 

 of our planet were all land, so that there was no watery vapour 

 in the atmosphere ; there would be no cyclonic storms, for they 

 are due to what Espy truly calls steam power ; — would the polar 

 depressions of the barometer be observed as they are in our 

 actual atmosphere? Mr. Clement Ley's reasoning seems to 

 require him to say that they would not ; I have no doubt that 

 they would. The causes which produce the west winds of the 

 middle latitudes (Maury's " counter-trades") would act as in our 

 actual atmosphere, and their centrifugal force, in rotating round 

 the poles, would produce a space of shallow atmosphere at and 

 around each pole, exactly like the depression at the centre of a 

 vortex of water, which would show itself, as at present, by a 

 depression of the barometer. 



I see in Nature of the same date that it is proposed to form 

 a meteorological observatory on Etna. . I hope the opportunity 

 may be taken of obtaining what is one of the greatest desiderata 

 in the present state of meteorology — I mean a set of comparative 

 observations of the barometer taken at two neighbouring stations, 

 one at the sea-level, and the other at a great height. One such 

 set, continuous or taken at short intervals, extending over a few 

 years, and accompanied by observations of temperature and 

 wind (the latter by self-registering anemometers), would probably 

 give more informrtion on the physics of barometric waves than 

 could be obtained by any amount of observations, all taken at 

 the sea-level. I have urged this in Nature before, but it is so 

 important I hope I may do so again. 



Joseph John Murphy 



Old Forge, Dunmurry, Co. Antrim, January 20 



Cyclone — Vertical Section. 



as a frustrum of a cylinder, which might also represent, when in 

 a state of gyration, a cone of the same diameter and forty feet high 

 in the centre. The contents of this space would amount to about, 

 in bulk, 1,094,785,668,000 cubic feet, representing a weight of 

 7o>339.979, 169,000 lbs of sea-water, which would have flooded 

 over a perfectly level district of a disc of about 700 miles in dia- 

 meter, or 39,270 square feet in area to the depth of one foot hori- 

 zontally. 



The Boomerang 



Referring to my letter on the " Boomerang " 

 which you were so good as to publish in Nature, 

 vol. xiv. p. 248, I may, perhaps, be permitted to 

 add a few more statements on the same subject. 

 Concerning the use of the boomerang by the 

 North Gippsland aboriginal natives, I have no 

 more to add, but I have acquired some informa- 

 tion in respect to its use among the blackfellows 

 of South Australia, which may be of interest. 



My informant is Mr. James, now a senior con- 

 stable in the Victorian police, but formerly, and 

 when I first became acquainted with him, manag- 

 ing a large cattle station at Blanchewater, on the 

 borders of the so-called Lake Torrens Basin. 

 Mr. James has had great experience among the 

 blacks of that district during many years both 

 before and after the time I first met with him, 

 during my second expedition into Central Australia. 



I quote Mr. James's statements to me just as I noted them :-— 

 "Among the blacks about Blanchewater the boomerang is 

 made for killing game. It is principally thrown among flocks 

 of ducks, pigeons, and water-hens. It is not used often for 

 fighting nor for killing kangaroo. They might use it in a row 

 when short of weapons, and if their adversaries were not more 

 than twenty or thirty yards distant. The blacks did not 



