NATURE 



[May 4, 188s 



violence of a storm arriving on our coasts, so that if 

 meteorology, or that branch of it termed weather fore- 

 casting, is ever to become an exact science, we must 

 endeavour to find out, by captive balloons or other- 

 wise, what can never be determined by registration 

 at the earth's surface alone, viz. the condition of the 

 atmosphere vertically as regards temperature and 

 humidity. 



The author concludes his theoretical investigation into 

 the mechanics of cyclones by a discussion of the causes 

 of their motion over the earth's surface. He first of all 

 shows that every cyclone possesses an inherent force 

 tending to urge it towards the pole of the hemisphere in 

 which it has been formed. This follows immediately 

 from the fact that the deflecting force due to the earth's 

 rotation varies with the cosine of the colatitude, and is 

 therefore greater on the polar than on the equatorial 

 side of a cyclone, a residual poleward component of force 

 being thus brought to bear upon every portion of the 

 cyclone. In addition to this, a cyclone, as soon as it is 

 generated, must partake of the general motions of the 

 atmosphere, which the author more especially deals with 

 in his "Meteorological Researches," Part I., to which 

 we have already made allusion ; and since the general 

 motions of the atmosphere are there considered to form 

 two great cyclonic systems round the poles, all ordinary 

 cyclones are simply cyclones within a cyclone, so that 

 their general motion of translation is partly the result 

 of the actual motion of the air in these large and per- 

 petual, though perpetually changing, cyclones, and partly 

 that of their inherent tendency to press polewards 



For example, as the author says, "in the trade-wind 

 latitudes the wind at the earth's surface is westward 

 and hence the cyclones in these latitudes are carried 

 westward, . . . and having a tendency towards the Pole, 

 the resultant of the two is a westward motion, inclined a 

 little towards the poles, or in the northern hemisphere a 

 motion about west-north-west. After having arrived at 

 the parallel of 30° or 35° in the tropical calm-belt, where 

 there is no westward motion, the progressive motion is a 

 Poarone mostly, but after progressing still nearer the 

 fole, into the middle and higher latitudes, the general 

 eastward motion of the atmosphere here, which is great 

 in the upper regions, carries now the cyclone toward the 

 east, and the direction of the progressive motion, which is 

 usually about east-north-east, is the resultant of this east- 

 ward motion and the motion round the Pole. All well- 

 developed cyclones, therefore, having their origin near the 

 equator, have mostly a progressive motion represented 

 by a curve somewhat in the form of a parabola havin" 

 as vertex in the tropical calm belt at the parallel of 30"° 

 or 35°." * 3 



It is moreover shown that the general motions of the 

 atmosphere must not only cause the cyclone to travel 

 more or less with them, but also affect the inclination of 

 the wind to the isobars, decreasing it in the front, and 

 increasing it in the rear part. 



With regard to further modifying causes, the author 

 favours the views of Clement Ley regarding the effect of 

 the distribution of aqueous vapour in determining the 

 direction in which a cyclone propagates itself. 



He does not indeed attempt to explain how they some- 

 times wander off on an entirely unlooked-for course, or 

 else remain stationary for some considerable period • 

 otherwise he might claim to have at least attempted a 

 solution of the entire problem on which weather science 

 depends. Clement Ley himself, in his admirable little 

 work,' recently published bv authority of the Meteoro- 

 logical Council, tells us that the reason why the course of a 

 cyclone cannot be exactly foretold is because " in the first 

 place the causes which determine the course of depres- 

 sions are not fully known ; in the second, place so far 



w'A.'Isto.' "' e Stndyand F ^ c ^ °f 'he Weather," by W. Clement Ley, 



as they are known, it is certain that the course of depres- 

 sions is generally related to the distribution of pressure 

 over a very large area." In fine before we kn6w how the 

 small cyclones are going to behave, we must in every 

 case know the form of the larger cyclones round whose 

 centres they travel. 



E. Douglas Archibald 

 {To be continued.) 



THE GIZZARD-CONTEATS OF SOME 

 OCEANIC BIRDS 

 "pHE following results of the examination of the gizzards 

 * of twenty sea-birds, which were caught by the officers 

 of this ship in the South Atlantic and Southern Indian 

 Oceans during the last quarter of 1S81, maybe of interest 

 to some of the readers of Nature. 



With one exception all the birds belonged to the Petrel 

 family— the Procellaridae— and fifteen of them were of 

 the well-known species -the Cape-pigeon or Cape-petrel 

 {Daptwn capeitsis). The most frequent of the gizzard- 

 contents of these twenty birds were the mandibles of a 

 cephalopod, which were found in eighteen instances ; the 

 otoliths of some small osseous fishes occurred in five 

 instances ; and some curious stony masses, varying in 

 weight from half a grain to five grains, were obtained also 

 in five instances. The other substances, which were ob- 

 served less frequently, were the vertebra; of a fish, feathers 

 Velellae, the horny rings probably of some crustacean, 

 and a small hard seed. 



With reference to the seed just mentioned, I should 

 observe that it was taken from the gizzard of a Cape- 

 pigeon, about 550 miles to the east of Tristan d'Acunha, 

 in the South Atlantic. The wide range of this species of 

 petrel is well known; we ourselves first observed this 

 bird rather to the southward of the island of Trinidad 

 which lies about 600 miles off the coast of Brazil • and 

 thence we traced it as far as the island of Amsterdam, in 

 the southern portion of the Indian Ocean. From our 

 own observation, therefore, it is quite possible that a seed 

 might be transported from Trinidad to Amsterdam, not- 

 withstanding that these islands are from five to six thou- 

 sand miles apart ; and Mr. Mosely's surmise {vide a foot- 

 note m Mr. Wallace's " Island Life," p. 250) that various 

 species of Procellaria and Puffinus may have played a 

 great part in the distribution of plants, and may to some 

 degree explain the similarity in the mountain floras of 

 widely distant islands, would appear to receive some 

 support from the single instance of this seed. With 

 regard to the kind of plants to which the seed belongs, 

 Mr. Moore, director of the Botanic Gardens, Sydney, 

 kindly informed me that it possessed no character suffi- 

 ciently distinctive to enable him to decide as to its 

 probable source. 



The stony masses found in the gizzards of five of the 

 birds, all of which were caught in the South Atlantic, 

 were of two kinds : one of the masses was of a dark 

 colour and homogeneous texture, and rather porous; 

 when heated it gave off black fumes with a smell of burnt 

 organic matter, and was fusible with soda into a black 

 glass ; the other masses had the appearance of greasy 

 quartz, scratching glass with ease ; but when heated in a 

 closed tube they blackened and evolved black fumes with 

 a powerful odour of burnt animal matter ; after the in- 

 cineration they became white, and with the blowpipe 

 were fused into a white glass after the addition of soda ; 

 no effervescence was exhibited on the application of an 

 acid. The behaviour of these masses under heat is verv 

 similar to that described by Mr. Darwin in his " Geological 

 Observations," in the case of a stony incrustation on St. 

 Paul's Rocks, deposited, as he considered, from water 

 draining through birds' dung. H. B. GUPPY 



H.M.S. Lark, Auckland, Februarv 28 



