190 



NATURE 



[June 30, 1881 



value of observations in soino degree if all those who have oppor- 

 tunities of making them would draw up their notes on some 

 regular and uniform plan. I do not presume t j submit a schcLne, 

 but would suggest the following points as being of some iui- 

 portance : — • 



1. Date, and hour of the day. 



2. Area of storm. If it assume the tornado form, give (a) 



length of the course, {b) breadth, (c) direction of motion, 

 (d) rate of progression. 



3. Physical features of the locality — (a) elevation, {b) moun- 



tains and plateaux, (c) rivers and valleys, (d) forests, iS:c. 



4. Temperature {a) before the storm, (l>) after the storm, and 



if possible to be observed (<•) changes during the storm. 



5. Barometrical readings (frequently taken during time of 



hailstorm). 



6. Wind — (a) direction near the earth's surface, {b) direction 



in the higher regions as indicated by the cloud motion, 

 (c) force. 



7. Preceded or followei by rain. 



8. Aspect of the clouds. Note if there be any appearance of 



two separate strata at dififeient elevations. 



9. Electrical phenomena. .Should 4here be lightning, note the 



relati m between the discharges and the fall of the hail — 

 whether the lightning precede the hail, or vice versa. 



10. Duration of the storm at one spot. 



11. Sound. Note if a peculiar noise precede tlie descent of 



hail. 



12. Conformation and size of the hailstones. 



13. General character of the weather before and after the 



storm. 

 Notes. — ( I ) The precise date of a hailstorm is an important point, 

 as it determines the period of their occurrence. Respecting the 

 annual period we hive the most conflicting testimony. Shortly 

 after the establishment of hail insurance companies valuable 

 statistics were published by those bodies. From particulars 

 furnished by the Farmers' Insurance Institute the following 

 table was drawn up ; — 



Hailstorms in January ... ... ... ... o 



,, February ... ... ... i 



March 



April 



May 



June 



July ... 



August . . . 



September 



October ... 



November 



December 



the result of five years' ob erva- 



Dalton gives the fillow 

 tions: — 



In January it hailed on 11 days. 



,, February ,, 7 »» 



„ March ,, 5 ,, 



,, April ,, S ,, 



,, May ,, II ,, 



,, June ,, 6 ,, 



,, July ,, 2 ,, 



,, August ,, I ,, 



,, Septejiber ,, 6 ,, 



,, October ,, 7 ,, 



,, November ,, 7 ,, 



,, December ,, 13 ,, 

 Giddy thus sums up twenty-one years' observations at 

 Penzance : — 



July I 



August o 



January 

 Feliruary 

 March 

 April ... 

 May ... 

 June ... 



September . 

 '. ctober 

 November . 

 December . 



43 



Thomson ("Introd. to Met." p. 174) gives the following as 

 the relative proportions : — 



Winter to all the other seasons as 45'5 to 54'S 

 Spring ,, ,, 29-5 to 70-5 



Autumn ,, ,, 22"o to 78'o 



Summer ,, ,, 3 'o to 97^0 



From a comparison of these tables we see that Dalton, Giddy, 

 and Thomson agree in making winter the season of maximum 

 hailfall, while the insurance statistics point to the opposite con- 

 clusion, the hailstorms in June and July being much in excess of 

 tho^e ill the other months of the year. I strongly suspect how- 

 ever that Dalton, and other observer.-, who have arrived at similar 

 results, included in their enumeration of hailfalls what we may 

 call, in absence of a better nane, winter hail. It is very unfor- 

 tunate that the word hail has in our language been used to 

 denote two entirely different phenomena, the French p'ele, or 

 hail proper, and grhil, or that small round powdery snow which 

 often falls towards the end of a snowstorm and in the early part 

 of a very frosty night. Grcsil has nothing in common with 

 grile. The one falls exclusively in winter, and the other, I 

 venture to say, as exclusively in .summer. 



(6) Dalton observed that the winds which brought hail- 

 showers in the north of England were always south-west, west, 

 or north-west. The wind often shifts erratically. Howard 

 mentions a hailstorm during which it was first east, then south, 

 afterwards west, again east, and finally west. Beccaria makes the 

 following singular statement : — " While clouds are agitated with 

 the most rapid motions, rain generally falls in the greatest 

 plenty ; and if the agitation be very great, it generally hails." 



I shall be glad to receive references to memoir> and papers on 

 the subject of hail, also particulars of storms, from any of your 

 readers who have them at hand. J. A. B. OLIVER 



Athenaeum, Glasgow, June 6 



How to Pievent Drowning 



In the discussion that Dr. MacCormac's letter has elicited, the 

 essential principle upon %\hich the whole art of swimming is 

 fundamentally based appears to have been overlooked. As Dr. 

 MacCormac says, tlie human body naturally floats in water, and 

 freely so in salt water ; but ho-di does it float, supposing the neces- 

 sary condition of buoyancy, the inflation of the lung-, is maintained? 

 If the limp, dead body of a man is thrown into water in this con- 

 dition it floats with the head and face immersed, but with that 

 1 art of the back just between the shoulders upward-, and just 

 bobbing out of water. This is a drowning position, and the first 

 bu-iness of swimming is to counteract the tendency to this posi- 

 tion, that is, to balance the bo.iy in such wise that the head shall 

 be upwards and the lower part of the face uppermost, in spite of 

 the natural tendency of the head to sink, it having a greater 

 specific gravity than water, or the average of the whole body. 

 Dr. MacCormac, in his letter (p. 166), says that "it is just as 

 easy, if we only knew it, to tread water as to tread earth." 

 Quite so ; but it is also about as difficult. No human being can 

 "tread earth" without training, the principal effort in thi- 

 training being directed to keeping the centre of gravity within 

 the base covered by the soles of the feet ; and in like 

 manner we must learn to keep the centre of gravity of the 

 body and the centre of its buoyancy in a perpendicular line 

 with mo.ith and nostrils in the air. I have been a swimmer 

 since I was eight years of age, and consequently swim as naturally 

 as I walk, and float ea ily in fresh or salt water, without any 

 treading or paddling of any kind ; but though I can thus lie 

 basking luxuriantly and motionless, I am just as unable to sleep 

 floating as to sleep standing upright. I have often tried, and 

 immediately I begin to doze my mouth is under water. The 

 effort of keeping the face upwards is as automatic and unconscious 

 as that of standing still on the ground, but there is an effort of 

 balancing nevertheless. 



I have taught many to swim, and my first lesson is on balancing 

 the body ; the easiest formula for attaining this power is to keep 

 the hands doum and look at the sky y;\\\\e. the chest is expanded 

 as much as possible by throwing the shoulders well back in 

 military attitude. Any man or woman of ordinary specific 

 gravity who can do this can float and breathe, but to do it, 

 simple as it is, requires practice or training, physical training of 

 the muscles, and cerebral training in order to acquire that 

 command of all the faculties without which there can be no 

 treading of water or other device for keeping the mouth and 

 nostrils in the air. If this were taught, not on paper, but in the 

 water, to everybody. Dr. MacCormac's object would be attained. 

 As it is, the human being compared with four-legged animals is 

 relatively as inferior to them in water as it is on land. The calf 

 or the colt walks a few minutes after it is born, the kitten or 

 puppy in a few days ; but the human infant only after many 

 months. W. Mattieu Williams 



Royal Polytechnic In titution, June 27 



