146 



NATURE 



\_Dcc. 16, I ! 



written because tbe Rev. Professor had written a very long one, 

 in which he applied this kind of bad reasoning in relation to a 

 bit of a leafy part of a tree found at Bournemouth in an Eocene 

 deposit. The leaves of his bit resemble those of Araucaria 

 Ciinniitgliami squashed ; nevertheless a thermometric virtue is 

 given to the fossil because this Araucaria is native in districts in 

 Eastern Australia. 



Self-satisfied with his recognition of the similarity of the 

 leaves, the Rev. Professor coolly assumes that he has made out 

 his species, and therefore demands the name of mine, giving me 

 a scolding before I could possibly let him have it. 



It is curious that the Rev. Professor should not have seen the 

 point of my letter, and the only explanation is that he was so 

 taken up with the incomparable value of his delicate "self- 

 registering plant thermometer." I did not believe in his dis- 

 covery, and my bamboo — never mind whence it came — was quite 

 as good in the method of argument as his so-called Araucaria. 

 No botanist would feel satisfied with the coneless evidence of 

 the Rev. Professor, and his genus is in doubt as well as his 

 species. With regard to this, Lindley stated years since that 

 Araucaria CinDiinghami is a "supposed species" in relation to 

 the Norfolk Island C.exccha. So the "self-registering ther- 

 mometer" has neither bulb nor stem, and the spirit or the mer- 

 cury represents the Rev. Professor's genius. He bids me plant 

 the bamboo in the sunny south-west. Not so ; it is the damp 

 soil and the shade M'hich have permitted the stems to grow up 

 to 10 feet 6 inches. He tells me that the bamboo grows in 

 China : that fact I had heard of before, and it has been strik- 

 ingly impressed on many generations of Celestials. Last week, 

 but too late for my purpose of immediate publication in Nature, 

 I learned that the bamboo is of the sub-genus Arundinacea, and 

 the species is falcata. Its natural habitat is in the temperate 

 Himalayas, where frosts, fogs, and north-east winds, such as 

 plague the Thames Valley, are unknown. 



Finally I believe that the so-called A. Cnnninghami has 

 grown of late years in the south of England. 



December 9 P. M.-\RTIN DuNC.\N 



Hailstorm in Dorsetshire 



At about 1.30 on the 25th of last November, with a strong 

 wind from the south-\^ est, this jDlace was visited by a hailstorm 

 which lasted about five minutes, accompanied by rain and violent 

 gusts of wind, and by a single vivid flash of lightning wliich m as 

 followed with scarcely more than an appieciable interval by the 

 thunder. 



The character of the hailstones which fell on the occasion, 

 and which I examined before they could have undergone any 

 important change induced by the higher temperature of the 

 surrounding air,' may be worlli noting ; for though they were not 

 of very unu-ual size, and in most respects scarcely departed from 

 what may be regarded as the typical condition of hailstones, they 

 exhibited some features not generally met with in so well-marked 

 a form. 



In their simplest condition their shape was that of a sphere, 

 and in every such case they consisted of a spherical nucleus of 



opaque white ice enveloped by a concentric shell of ice per- 

 fectly transparent and Iiomogeneous, showing none of the radial 

 strix- often met with in hailstones (Fig. i ). The largest measured 

 about half an inch in diameter, the nucleus having a diameter 

 of about a quarter of an inch. The appearance of the opaque 

 white nucleus surrounded by its thick crystal-clear envelope was 

 very striking and beautiful. 



In many cases two such hailstones were united firmly to one 

 another, doubtless by a process of regelation after contact. In 

 some of these llie transparent envelope was continuous around each 

 of the nuclei in the plane of contact ( Fig. 2). In others it w as here 

 deficient, and the two nuclei were then in immediate contact with 

 one another(Fig. 3). The difference thus presented is not without 

 significance as affording evidence that there are two distinct 

 conditions under which the union of hailstones by regelation 

 may occur ; for it is probable that in the former case the contact 

 and regelation had ^laken place directly between the nuclei 



while as yet free from the investing shell of clear ice which had 

 afterwards formed around the twin nuclei ; while in the latter 

 case the envelope had already existed before the contact and 

 regelation of the hailstones. 



Another frequent occurrence was the presence of one or two 

 little piriform offsets, which projected from the surface of the 

 hailstone, and were, like the envelope itself, formed of clear homo- 

 geneous ice (Fig. 4). In a paper published in the Proc, Asiatic 

 Society for June, iSSo, to which my attention has been called 

 by Mr. Scott of the Meteorological Office, very similar club- 

 shaped projections of transparent ice are described by Mr. 

 Blanford in large hailstones figured by Col. Godwin-Austen as 

 having fallen at Calcutta in March, 1S77. 



It is possible that in these cases the projections had originally 

 the form of crystals, and that their faces and angles had been 

 rounded off in passing through a warmer region of the atmo- 

 sphere, such radiating crystals of ice not being unknown. In 

 a memoir by Abich (" Ueber Kugel Hagel im Unterem Kau- 

 kasus," Vienna, 1879), for a knowledge of which I am also 

 indebted to Mr. Scott, an account is given of certain very large 

 hailstones which fell at Tiflis in Georgia, and had large ice 

 crystals radiating from the surface. Geo. J. Allman 



Ardmore, Parkstone, Dorset, December 1 1 



Sargassum 



I KIND in Nature, vol. xxiii. p. 70, a short report on my 

 paper, "Revision von Sargassum," with several objections, 

 which I believe to be erroneous. It is said that the fragments 

 occurring sometimes on the open sea, the so-called Sargassum 

 bacciferum, should have a bright yellow colour. Not long ago I 

 received fresh samples thereof from the Sargasso Sea, which are 

 not yellow at all ; these fragments are never bright yellow, but 

 of the same brown, varying to yellowish colour as decaying 

 Fuciis vesicidosus. I observed the latter, for instance, in this 

 condition in several fjords of Norway, where I found broken 

 Fucus in greater quantities than ever I did Sargassum in the . 

 open sea between England and the West Indies. 



Mdcrocystis pyrifera shows always stem and leaves entangled 

 in a ball, if broken and swimming in the open sea {vide p. 235 

 of my treatise), and the Sargasso fragments of the open sea are 

 also often entangled in compact balls, as Sir Wyville Thomson 

 states ("The Atlantic," i. 194), and as it may be seen on my 

 phototypic table. Fig. I. 



If the floating Sargassum should have no reproductive organs, 

 this would be no difliculty, but rather a confirmation of my 

 views on the fragmentary nature of swimming Sargassum, for a 

 particular pelagic species could not be without reproductive 

 organs. Besides there have been found "with certainty " some- 

 times samples in the open sea with reproductive organs, and I 

 gave an explanation of their seldom occurrence by want or 

 breaking off of the air-vesicles. The writer on my paper is 

 mistaken in comparing Macro :ystis and Fucus with Sargassum, 

 for the air-vesicles and reproductive organs of Sargassum are 

 separate from the leaves and isolated on thin stalks, which 

 break off easily, while those of Fucus and Macrocystis are never 

 separate, but in the nuddle of the leaf or on the base, or on the 

 broad end of the leaf or thallus. Therefore swimming Sargassum 

 is found often without reproductive organs, and its air-vesicles 

 are often broken off, whilst on Macrocystis and Fucus such a 

 separation is not possible. Having refuted those objections, and 

 having also brought in my paper many more arguments against 

 the existence and vegetation of Sargassum bacciferum than 

 there are mentioned in the short report, I hope that my results 

 on Sargassum will now generally be accepted, 



Leipzig-Eutritzsch, December 4 Otto Kuntze 



Note on an Acoustical Constant 



The number of vibrations executed in a second by a stretched 



string is generally represented in the text-books by a formula 



expressing the method of its variation with the determining 



circumstances, such as — 



dl W 1' 



where d is the diameter, / the length, s the specific gravity of the 

 string, and T the tension or stretching force, but the absolute 

 number of vibrations is not generally given by the formula. 



