lilay 6, 1880] 



NATURE 



1 r 



Protection against Mosquitos, Flies, and Blight 



Mr. IIagen's letter on the destruction of insect-pests (Nature, 

 vol. x.xi. ji. 611) induces me to make generally known an absolute 

 preventive of the bites of mosquitos, gnats, of green-fly in the 

 vhiery, blight in the garden, and a protection to animals from 

 these ■' in>ect-pests." A few years ago I had some peach-trees 

 which, being on a wall exposed to draught, were annually 

 blighted. One died, and the new wood of the others was not 

 more than a hand's length. A scientific friend advised me to 

 try a weak solution of quassia to water them w ith, and the suc- 

 cess was complete. Blight was prevented. The first year the 

 trees bore well and the new wood was elbow-length or more. 

 I next tried quassia in the vinery. Instead of lime-washing the 

 walls to get rid of the green-fly, one watering with quassia dis- 

 missed them in a day. My head-gardener, who had previously 

 much experience in nursery-grounds, wondered that he had 

 never heard of it before. He now uses it in all cases as a pro- 

 tection from flies and blight. The dilution goes a long way : 

 one pound of chips of quassia-wood boiled and reboiled in other 

 w ater until he has eight gallons of the extract for his garden- 

 engine. He find.s it inadvisable to use it stronger for some 

 plants. This boiling makes the quassia adhesive, and being 

 principally applied to the underleaf, because most blight settles 

 there, it is not readily washed off by rain. Quassia is used in 

 medicine as a powerful tonic, and the chips are sold by chemists 

 at from sixpence to a shilling a pound. The tree is indigenous 

 to the West Indies and to South America. 



And now as to gnats and mosquitos. A young friend of 

 mine, severely bitten by mosquitos and unw illing to be seen so 

 disfigured, sent for quassia-chips and had boiling water poured 

 upon them. At night, after washing, she dipped her hands into 

 the quassia w'ater and left it to dry on her face. Tliis was a 

 perfect protection, and continued to be so whenever applied. 

 The pastilles sold in Florence and elsewhere, which are vaunted 

 to be safeguards against mosquitcs, are, from my own experience, 

 of no u-e. 



At the approach of winter, when flies and gnats get into 

 bouses and sometimes bite venomously, a grandchild of mine, 

 eighteen months old, was thus attacked. I gave the nurse some 

 of my weak solution of quas-ia to be left to dry on his face, and 

 he was not bitten again. It is innocuous to children, and it 

 may be a protection also against bed insects, w hich I have not 

 had the oi'portunity of trying. When the solution of quassia is 

 strong it is well knowni to be an active fly-poison, and is mixed 

 w ith sugar to attract flies, but this is not strong enough to kill at 

 once. If it be true that mosquitos have been imported into one 

 of the great hotels in the srjuth-west of London, it might be very 

 useful to anoint some of the furniture with it. Then a strong 

 solution with sugar set about the rooms ought to clear them out. 



Oatlands P.ark, Weybridge Wm. Ch.^ppell 



Immersion of Iron and Steel in Acidulated Water 



In Nature, vol. xxi. p. 602, I have read an interesting 

 account of Prof. Hughes's experiments on the change produced 

 in iron and steel wire by immersion in acidulated water. 



May I ask you to draw the Professor's attention to my 

 experiments on this subject, 'jide Proceedings of the Literary 

 and Philosophical Society of Manchester, January 7, March 

 4, December 30, 1873; January 13, March 10 and 24, 1874; 

 and Proceedings of the Royal Society, No. 158, 1875 ; and a 

 short article in Nature, I think. 



It has long been known to manufacturers of iron wire that 

 iron becomes brittle after immersion in dilute sulphuric or hydro- 

 chloric acids. I believe, however, that I was the first to show 

 that this change was due to occluded hydrogen, and by a careful 

 series of experiments to determine approximately the percentage 

 alteration in the breaking strain and elongation at the moment of 

 rupture produced by occluded hydrogen in — 



{(2) Ordinary or puddled iron wire ; 



(/') Iron wire manufactured with charcoal instead of coal ; 



(c) Mild or Bessemer steel ; 



(d\ Cast steel. 



I also found an increased electrical resistance in wire containing 

 occluded hydrogen, though subsequent experiments have led me 

 to believe that the numbers I first published were too large. 



My papers also called attention to the diflTusion of hydrogen 

 in iron wire beyond the part immersed in acidulated w ater ; the 

 increase in the length of wire charged with hydrogen and some 

 other phenomena. 



The whole subject of the occlusion of hydrogen by metals is 

 one of great interest, and the scientific world will be glad if an 

 accomplished experimenter like Prof. Hughes turns his attention 

 to the subject. William H. Johnson 



The Ferns, Bowdon, near Manchester, April 26 



Stone Arrow Heads 



The interesting investigations of Mr. Redding on the method 

 of making the above objects, as referred to in Nature, vol. 

 xxi. p. 613, have been somewhat anticipated by Mr. Paul 

 Schumacher, "Methods of making stone weapons," Bull. U.S. 

 Geol. and Geog. Survey, vol. iii. p. 547, 1877, which again was 

 a translation from an earlier publication in Archiv Jiir Anthro- 

 fologic,\ vol. vii. p. 263. Mr. Schumacher's information was 

 derived^from the last arrow-maker of a tribe nf Klamath Indians, 

 and appears to correspond generally with that obtained by Mr. 

 Redding from the representative of another tribe in the same 

 region. Mr. Schumacher states that obsidian is not the only 

 stone used, but chert, chalcedony, jasper, agate, and similar 

 stones of conchoidal fracture. "The rock is first exposed to 

 fire, and, after a thorough heating, rapidly cooled off, when it 

 flakes readily into sherds of different sizes under well-directed 

 blows at its cleavage.'' The process is also illustrated in Mr. 

 Schumacher's paper. Superior stone mortars are often found ia 

 use amongst these Californian Indians, who deny their capa- 

 bility of making such objects, and account for their possession 

 as "finds" either on the surface or beneath the earth, and 

 describe them as the w^rk of another and previous race. 



W. L. Distant 



Derwent Grove, Eat DuKvich, May i 



The Mode of Suclding of the Elephant Calf 



In some of the accounts recently published of the birth of an 

 elephant in a menagerie in America it is stated that up to this 

 time naturalists had always believed that the elephant calf 

 obtained its mother's milk by means of its trunk, and not directly 

 by the mouth. 



Whether this be the case or not, Aristotle was certainly an 

 exception, as the following passage from the twenty-seventh 

 chapter of the sixth book of his " Hi-toria Anim.alium"' (Ed. 

 Eekker, Oxford, 1S37) clearly proves — 'O hi tniiixvos, Sraf 

 ■yiin)Tat, SriXd^cL Tea uruVari, ou Tm fLvKTfjpl, Kol HaSiC^i "al /SAeVet 

 ei/ehs yivurieds. — "And the calf, when it is born, sucks with 

 its mouth and not with its trunk ; and it both walks and sees 

 as soon as it is born." J. C. G. 



May 3 



The Tay Bridge Inquiry 



In the Pall MaU of April 21 appeared a report of the 

 evidence of Mr. Henry Law, C.E., in the Tay Bridge inquiry. 

 In this report Mr. Law is made to say: "The heavy girders 

 would fall more rapidly than the carriages ; a train moving for- 

 ward at a great speed would not fall so rapidly as a quiescent 

 structure." 



I have been induced to ask your insertion of this note in 

 Nature in the hope that some of your readers who are at home 

 in such matters may confirm or contradict these statements. A 

 person with a mere elementary knowledge of dynamics would 

 disbelieve the latter of them, and would doubt that the forirer 

 has any /ra.V/ra/ truth. Q. C. 



Queenwood College, near Stockbridge, Hants 



Yeast and Black Beetles 

 In what form should yeast be applied for the destruction of 

 black beetles ? If Prof. Lankester will show us how to exter- 

 minate them he will earn the gratitude of every 



London Householder. 

 27, Marlborough Hill, N.W., May I 



Suez Canal Rock Salt.— Dr. Ralton wishes to know 

 where information can be obtained en the subject of the rock 

 salt Leds which were cut through in constructi;ig the Suez Canal. 



SoDic Chloride Crystals.— Dr. Ralton asks, what is the 

 action of urea in modifying the crj-stal form of sodic chloride 

 crystals, referred to by our reviewer of Dr. Ord's book ? 



[Sodium chloride usually crystalli-es in cube; ; it is stated, 

 however, by Prof. Maskeiyne in a lecture before the Royal 



