142 



NATURE 



{yune 1 6, 1 88 1 



locality being in Kent. It is therefore of the highest importance 

 that one should know for certain whence the gravel has been 

 derived that one sees on tlie roads. 



I live in an implementiferous district, and find Pala;olithic 

 implements in the Highbury and Clapton gravels ; but a visitor 

 would make a fatal mistake if he supposed that all the gravel on 

 the roads about here belongs to the district. Sometimes many 

 tons of gravel are brought here from Waltharastow ; at other 

 times from Ware or Hertford ; sometimes from Dartford, and 

 from other places. Unless, therefore, the greatest possible care 

 is .taken in ascertaining the exact locality whence the ballast 

 comes, mistakes are certain to occur. 



The lowest gravels about here are unproductive of the works of 

 primaeval man, with the exception of, at times, a stray flake or 

 two, probably derived from a higher level. The evidence that 

 I have seen in the lower gravels round London points to the 

 correctness of the conjecture made by General Pitt- Rivers, that 

 the Paleolithic age had passed away before the lower parts of 

 the Thames Valley were excavated. 



WORTHINGTON G. SMITH 



I2S, Grosvenor Road, Highbury, N. 



How to Prevent Drowning 



I HAVE read with some interest Dr. MacCormac's letters on 

 the subject of water-treading as means of preventing drowning. 



I am sorry that I cannot agree with him, as it would be 

 decidedly a matter of congratulation if some practical means of 

 diminishing the number of casualties from drowning were found. 

 Personal experience, however, prevents my agreeing with Dr. 

 MacCormac. 



I am a tolerably good swimmer, can swim in all the diflferent 

 fashions, but I can neither float nor tread water. 



Shortly after Dr. MacCormac's first letter appeared I went to 

 swimming baths with a view of putting the matter to the test. 

 I had carefully read Dr. MacCormac's letter, and determined 

 to give it a fair trial. I minutely observed all his directions, 

 and invariably sank every time I tried his plan. 



Now it must be remembered that I am a swimmer, and so far 

 as swimming goes, perfectly at home in the water. Moreover, 

 I was not in the least flustered. When I sank I made no 

 attempt to rise again by swimming ; I remained in what Dr. 

 MacCormac would call the orthodox positioi for treading v\ater, 

 only opening my eyes in order to see whether I was ascending 

 or descending. As however I found that I continued to do the 

 latter until I reached the bottom of the bath, and there seemed 

 to be no probability that I should rise without some further 

 effort, I was at last compelled to make this effort. 



This was the course of affairs every time I made the attempt. 

 Moreover, whenever I essayed to float on the surface, although 

 I carefully assumed the correct position, threw my head well 

 back, and took the deep inspiration, the result was the same. 



Arguing from these facts, it seems to me pretty clear that it is 

 not everybody who can tread water or float. Why this is so, 

 appears to me to lie in the fact that the human body is not 

 always lighter, bulk for bulls, than water. Perhaps with plump 

 children and others with plenty of adipose tissue about their 

 frame this may be the case, but with spare people who consist 

 mainly of muscle and bo:ie, the specific gravity must be greater 

 than that of water. The bady of a fish when the animal is dead 

 will sink until decomposition sets in and causes it to float. 



For these reasons I fear that Dr. MacCormac's suggestion 

 will not be found of so much practical use as he hopes. The 

 apparent ease of tlie process described by Dr. MacCormac may 

 in itsel' be the cause of rash proceedings by those who cannot 

 swim, and may so lead to greater loss of life, the very evil which 

 the suggestion is intended to diminish, 



W. Henry Kesteven 



401, HoUoway Road, N., June 7 



On the Continent the facilities are greater than in England, 

 where factories and steam-boats spoil the pleasure of swimming, 

 and everybody is well aware that all can float upon fresh 

 ■water witJiout assistance from their hands and feet. It is what 

 in the Paris swimming-schools is called "faire le mort. " 



Anybody — stout, lean, cripple, halt — is able to do so, and I 

 taught, myself, a poor little hunchback how to perform this easy 

 feat ; but his deformity placing hi n in a state of unstable equi- 

 librium, he was obliged to keep his arms stretched at an angle 

 from 45° to 60°. 



Some minutes are sufficient in fresh water to make a proficient 

 and a live "mort." The way to do it is very simple, and Mr. 

 MacCormac described it very exactly, with the omission of some 

 particulars relating to the way of breathing, which had no direct 

 reference to his chief and beneficial topic, " treading water." 



He who wishes to "faire le mort" must first draw a deep 

 breath, and keep it, then put himself on his back, with his head 

 thrown backwards, as recommended by Mr. MacCormac, and 

 allow his limbs to droop slackly w ithout any stiffness, no matter 

 in what position. 



The body will sink at first under water, but it will immediately 

 rise nearly on a level with the surface, the only parts quite free 

 from water being the chest and the nose and mouth, around 

 which the water describes an oval, whilst the eyes are at times 

 over, at times under, water. 



The " mort " can remain floating in this way as long as his 

 breath allo\vs, thongh it is better not to wait longer than two 

 or three seconds, to avoid fatigue ; then he must quickly emit it, 

 draw another deep breath, and keep it again. 



The body sinks as before, rises immediately, regaining its 

 floating position, nose, mouth, and chest emerging again from 

 water. 



This can be continued for hours together without the least 

 motion of legs or arms, as your readers will be able to verify for 

 themselves, either at the Pont Royal or Ligny swimming schools, 

 on their visit to the Paris Exhibition of Electricity. 



Jersey, June 5 Chatel 



P.S. — I ought to add that whilst floating on fresh water the 

 body is not quite on a level with the surface, but from the chest, 

 that is out of water, to the toes, which are about six or eight 

 inches under water, figures an inclined plane, the slope of 

 which varies with everybody, and that any attempt to bring the 

 toes on a level with the surface makes the body sink. On the 

 contrary, the deeper the head is sunk backwards under water the 

 more the body emerges. 



Auroric Light 



June 6, faint lights, especially to the northward, between 10 

 and 12 ; smart frost. 



June 7i at 10, masses of purplish light rising from the north- 

 east and congregating about the zenith ; pencils of greenish 

 yellow and wliite rising to the north ; these continued up to 12, 

 after which no observations were made ; very smart frost, which 

 bit the potato stalks. 



June 7, from 10 to 12, well-marked and at times brilliant 

 columns, pencils, and masses of red rising all round the heavens 

 at intervals, and congregating at the zenith ; a moot severe white 

 frost that burnt up all the potatoes on the valley flats and on the 

 uplands. At 5.30 on the 8th the frost was so thick that the 

 ground had tlie appearance as if it had sno\\ed during the night. 



Ovoca, Ireland, June 10 G. H. KiNAHAN 



A Singular Cause of Shipwreck 

 In Nature, vol. xxiv. p. 106, you mention a " singular case 

 of shipwreck " caused by waves and spray freezing on a steamer 

 and sinking it by its weight. Cases of this kind caused by frozen 

 spray alone are known near the east coast of the Black Sea. 

 North of 44°, where the mountains are not very high, an ex- 

 ceedingly strong and sudden north-east wind is frequent, quite 

 similar to the Dalmatian Bora, and called alike. It descends at 

 a certain angle to the sea, raising a great quantity of spray. In 

 winter this spray immediately freezes, and ships may sink by its 

 weight. On January 25, 1S48, a war-ship, anchored in the 

 middle of the Bay of Noerrossiisk, sank in this manner. As the 

 weather was fine before, a great part of the crew were ashore, 

 and the storm arrived with such suddenness that the ship sank 

 from the weight of the frozen spray. On account of the bora 

 this coast is avoided by merchant-ships in winter, and visited 

 only by a line of steamers subventioned by the Government. 

 St. Petersburg, June S A. Woeikof 



OBSERVATIONS ON THE HABITS OF ANTS 



ON Thursday (June 2) Sir John Lubbock read a further 

 paper on this subject at the meeting of the Linnean 

 .Society. He said that in one of his former papers 



