HARDWICKE'S SCIENCE-GOSSIP. 



23 



" Peculiar Hailstones." — In "Nature," vol. 

 xv., at page 163, your correspondent, Alex. Johnstone, 

 F.R.S.S.A. (in the last number of Scienoe-Gossip), 

 will find, I think, a satisfactory answer to his 

 enquiries regarding hailstones. The article in 

 question is an abstract, with illustrations, of a paper 

 "On the Manner in which Raindrops and Hailstones 

 are formed," by Professor Osborde Reynolds, M. A., in 

 which the author endeavours by theory and experi- 

 ment to explain the true nature and mode of formation 

 of these productions. — J. A. Osborne, M.D., Milford 

 Letterkcnny. 



Hailstones. — About nine or ten years ago I 

 observed that the form of hailstones was altogether 

 different to what I had in my earlier days been taught 

 to assume. I had always been under the impression 

 that they were spherical, in fact, minute blocks of 

 ice — frozen rain drops. On the occasion of my 

 enlightenment, I was in a field when a heavy hailstorm 

 took place. This admitted of my seeing more perfect 

 specimens than if I had been in the street, or on a 

 public highway, as there was less probability of their 

 being broken in their fall. The enormous size of the 

 stones first attracted attention, but upon examining 

 them, it was also found that they were conical with a 

 smoothish rounded base. The sides of the cone were 

 striated towards the apex. Many of the cones had 

 broken apices, but sufficient was left to indicate their 

 complete form. Those which were perfect began to 

 melt first at their apex, the portion last to melt being 

 the rounded base. It is believed that this peculiar 

 form is due to the nucleus (a frozen ice particle) 

 passing from the upper portion of a frozen cloud or 

 fog. In its descent it overtakes and adds to itself 

 other ice particles, these form the originating elements 

 of the hailstone. By continued accumulation of 

 particle and pressure on the edges of the base, they 

 begin to round, until eventually it partly turns over 

 and forms the commencement of the cone which is a 

 rapid process. There is much assumption in this 

 theory, but there is evidence of its practicability from 

 the smoothness of the base, the striae of its sides, its 

 conical shape and the melting of the apex (the last 

 formed part) before other portions. The firmness of 

 the hailstone is proportionate to its size. The larger, 

 the firmer, and the harder its base is to its apex, 

 the larger, the heavier, and the greater the speed it 

 will travel through the cloud. The size to some 

 extent infers the depth or density of the cloud 

 through which it has passed, perhaps both. The 

 conical shape of the hailstone is well known, having 

 been seen by other observers. Since first seeing it I 

 have often pointed its shape. — Matt. Hedley, F. R. C. V.S. 



The Corixa in the Aquarium.— This insect 

 forms a very handsome and interesting object of an 

 aquarium. It is closely allied to the water boat-fly 

 (Notonecta glanca), and is very abundant in our 

 ditches ; in fact much more so than the latter. I 

 have several in my aquarium, and they are literally 

 the life of it. I caught them from the bridged-over 

 part of a ditch, when fishing for minnows and 

 sticklebacks, and where the water is nearly in 

 darkness. This suggests that they are fond of dark 

 nooks. Unlike its relation the boat-fly, it swims with 

 its back uppermost as do other aquatic insects. Its 

 longest pair of legs are not the last as in the boat-fly, 

 but the middle. It is so eccentric in its habits-, that 

 its actions often provoke mirth. I have closely 

 studied it for seme time past, and find that it 

 frequently has to rise to the surface for a fresh supply 

 of air which it does by a series of vigorous darts, and 

 when it has obtained that supply, it regains the 

 bottom by still more vigorous darts, in consequence 



of its increased buoyancy. So great is its buoyancy 

 when charged with air that I have seen one raise to 

 the surface a dead stickleback which must have 

 weighed more than ten times the weight of the corixa. 

 When it has descended to the bottom (a task which 

 is only performed with the greatest of difficulty, 

 judging from the zig-zag course the insect is compelled 

 to pursue) it clings to the nearest stone or pebble, 

 and stretches out its two flattened elongated legs, 

 and remains in this peculiar position for some time. 

 I am of opinion that the function which these 

 members now perform is analogous to that performed 

 by the poisers of a fly, viz. to balance the insect. 

 After it has remained in this position for some time 

 it performs a number of very comical spasmodic 

 movements by quickly passing its two oar-like legs 

 over its back, and as quickly withdrawing them. To 

 the ordinary observer, this is done by the insect, 

 probably for mere pleasure. A close observer, 

 however, detects in these very peculiar motions an 

 object. This object is nothing less than to break up 

 and set free parts of its air-bubble which most likely 

 the insect finds renders its body too light. Its under 

 surface where the air-bubble is, looks like a globule of 

 quicksilver. The facility with which it bends its legs 

 in almost any direction is very striking (I mean its 

 middle pair). I Jhiink its food consists of the 

 disintegrated particles of algae, which I have in the 

 aquarium, and which by some means or other have 

 become separated from their respective plants. 

 Should my surmise prove correct, then the corixa 

 will not only be found a pretty and interesting object 

 of the aquarium, but also a useful member of it. — 

 Arthur Ay ling. 



NOTICES TO CORRESPONDENTS. 



To Correspondents and Exchangers. — As we now 

 publish Science-Gossip earlier than heretofore, we cannot 

 possibly insert in the following number any communications 

 which reach us later than the 8th of the previous month. 



To Anonymous Querists. — We receive so many queries 

 which do not bear the writers' names that we are forced to 

 adhere to our rule of not noticing them. 



To Dealers and others. — We are always glad to treat 

 dealers in natural history objects on the same fair and general 

 ground as amateurs, in so far as the " exchanges " offered are fair 

 exchanges. But it is evident that, when their offers are simply 

 disguised advertisements, for the purpose of evading the cost of 

 advertising, an advantage is taken of our gratuitous insertion of 

 "exchanges" which cannot be tolerated. 



We request that all exchanges may be signed with name (or 

 initials) and full address at the end. 



W. White. — Apparently your nuts belong to Juglandaceae, 

 and are probably Carya amara or porcina. 



E. Lamplugh (Hull). — You cannot do better than obtain 

 Dr. Cathcart's new ether microtome, manufactured by Mr. 

 Charles Coppock, 100 New Bond Street, to whom write for its 

 "illustrated description." 



A. L. — For life-history of, and experiments on the common 

 liver-fluke, see paper by Professor Thomas in " Quarterly 

 Journal of Microscopical Science" for 1882. A good popular 

 paper on the subject was also written by Mr. George Dowker, 

 F.G.S., of Canterbury, a few years ago. A good description of 

 the earthworm will be found in one of the volumes of " Science 

 for All." 



R. H. W.— You will find a good account of Stonehenge in 

 the Guide to that place, to be obtained at Salisbury railway- 

 station ; or a longer one in Ferguson's " Rude Stone Monu- 

 ments' in Great Britain"; for an account of bone caves, see 

 Professor Boyd Dawkins' work on " Cave Hunting." Dr. Hicks' 

 address on " Bone Caves," will doubtless be published in the 

 4n=iJHUJsactions of the Society. 



E. E. Turner (Dublin).— Get Thome's " Botany," edited 

 by A. W. Bennett, and published by Longmans. It will 

 exactly meet your wants. 



R. C. — We do not recognise the specimens forwarded to us. 

 Please send fuller details. 



Ballywilliam. — You will find a good account of the Eu- 

 calyptus in the " Treasury of Botany." It has been planted 

 in Italy in order to drain the marshes. Its leaves give off a 

 great deal of moisture. The Eucalyptus is sensitive to frost, 

 and will not prosper where the nights are irosty. 



