• KNOWLEDGE • 



[Feb. 2. 1883. 



^y^^i^^z^i^v^rr^ 



" Let Knowledge grow from more to more." — Alfrkd Tennyson. 



iLftuiS tc ifte (ZtliitDr* 



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 Office, 74, Great Queen-street, W.C. If this is not attended to, 



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 payable to Messr.s. Wyman & Sons. 



The Editor is not responsible for the opinions of correspondents. 



No communications ARF, answered by post, even THOUGH STAMPED 

 AND DIRECTED ENVELOPE BE ENCLOSED. 



STINGING TREES. 



[698] — It may be interesting to some of your readers to know 

 that stinging trees are not confined to Australia alone. 1 have fre- 

 quently seen them .and felt them also in Kansas, U.S. 



I can hardly describe them, though, as trees, never having seen 

 them more than five or six feet high, yet they were quite distinct 

 from weeds. They seemed to flourish principally in the vicinity of 

 water, and we often came into contact with these unpleasant bushes 

 after bathing in the streams. The sting was in the leaves, bnt by a 

 remarkable arrangement of nature, these bushes appeared to be often 

 infested with caterpillars, which ate the leaves ofl'. At first, on 

 running against the bushes, we thought that the caterpillars stung 

 ns in some way, bnt on experiment we found that it was the leaves 

 themselves. The effects of the sting were very similar to bad 

 mosquito bites. 



I am sorry I cannot give you the Latin name, as I am not well 

 versed in botany. Percy Elbutt. 



Croydon, S.E. 



STAYS AND STATUES.— WINTER RARITIES. 



[699]— I note in your issue of January 12, a note to " Stays 

 and Statues " in which you say you may perhaps omit much which 

 you have written on the artistic aspect of the matter. 



Please dori't. Even if argument and evidence from statues, &c., 

 has no force with "Observer," it most probably has with numbers 

 of your readers who may profit by it, and you are not writing for 

 " Observer " only. 



I can supplement Mr. R. W. Smith's communication by stating 

 that I yesterday saw an apparently perfect specimen of the peacock 

 butterfly. 



In our open garden here we have some snowdrops in full blossom. 



W. Grandv. 



CHIRPING SPIDER. 



[700] — Can you, or any of your readers, tell me if there is a 

 British chirping spider ? I have long been perplexed, in the still- 

 ness of midnight, by a scratching, ticking, or chirping sonnd, 

 repeated with great regularity from a dozen to perhaps fifty times 

 in succession, ai)parently in the top of a low cupboard in the corner 

 of my sitting-room. I had begun to suppose it either some very 

 pertinacious wood-worm, or else the cooling and shrinking of the 

 wall into which the cupboard is built after a fire in the next housr 

 had gone out; but this evening the door stood a little open, and 

 the noise was louder. Quietly inserting a candle and my head, I 

 found the chirping silenced, even without the candle. Any 

 alteration of the light by the movement of my body in the 

 doorway silenced the chirping. However, after a long, patient 

 kneeling with my head in the dark cupboard, I heard the scratch, 

 scratch, sci-atch, close to my ear. I withdrew, and it ceased. 

 Returning with a match, I found my jiatienco again rewarded. 

 After very definitely locating the sound, I struck my match, and 

 lo and behold ! a small dense cobweb, consisting of a short tube 

 above and two spreading arms below. As I brought the fiamo 



within two inches of the wob, the chirping, which had been silenced 

 by the match, broke out with three violent rapid notes, and I with- 

 drew, fearing to disturb my guest. Ho has siuco been at it as 

 heartily as ever. He has been therr, I should say, at least a year. 

 The lupboard is seldom opened— perhaps once a fortnight, but occa- 

 sionally not at all for a month — so the supply of flies must be small. 

 There were the remains of some insect in a corner of the web. 



D. M. 



ALTERATION IX COAST-LINE. 



[7ul] — There are certainly some important and curio'.is queslioijs 

 that 11 >'ht be raised as to past changes in the co^ist-liuo betweeu 

 the Wel-ih coast at the mouth of the Dee and the Ribble; but your 

 correspondent, H'sett, in a letter in your number of Dec. 29 

 (No. 673), does not appear to me to offer any contribution towards 

 sonnd conclusions on the subject, as he is incorreit in the facts 

 from which he infers that " the sea has receded along the coast of 

 Lancashire, from the Mersey almost to Preston." Tiic ground on 

 which he bases this conclusion is that "the whole country ior 

 miles is as flat as the ])roverbial pancake, and it can be at once seen 

 that all this hand, which is entirely made up of sand, must have 

 been gradually formed by the retrocession of the sea." It is 

 quite true that the country between the Mersey and the Ribble 

 is flat, but it is not true that it is composed entirely, or even 

 principally, of sand. It is mainly composed of peat — the sand is a 

 mere fringe bounding the sea-coast, varying slightly in ^vidth, but 

 nowhere much exceeding a mile, and in some places the sand has 

 covered land formerly cultivated. There are, no doubt, changes 

 taking place, as is usual in all flat coast-lines, and on part of the 

 coast-line to the west of Sonthport the sand is certainl3- encroach- 

 ing on the sea, and a new line of sand-hills is in process of forma- 

 tion outside the present line ; but to tliL' east of Southport there is 

 no evidence of any such process going on, even if the reverse is not 

 the case. There is, it is true, a sand-bank oft the Southport coast, 

 separated from the end of the pier by a deep channel ; but it is 

 quite incorrect to speak as if the outside of that bank were the 

 coast-line. The sands off the coast from the mouth ot the Dec to 

 the mouth of the Ribble have changed much within living memoi'V, 

 but the changes are no duubt due to varying ocean currents, and 

 not to the encroachment of the laud on the sea ; and Southport is 

 certainly not at present more likely to become an inland town than 

 it was fifty years ago. 



A much more difficult and interesting question than the present. 

 changes in the sands is how to account for the remains of sub- 

 marine forests in the estuary of the Mersey — a fact of which yom 

 correspondent is apparently not aware. A Southport Resident. 



(Pur iWattjtmatical Column, 



A PRETTY PROBLEM. 



A CORRESPONDENT ("Taranaki") some time since asked for 

 a solution of the following problem, and we gave two solu- 

 tions, both analytical. Another correspondent, " J. C. S.," gives 

 the following very pretty geometrical solution : — 



Theorem. — Jf tangents P P, F Q, he drawn to a circle from F, the 

 point of intersection of two opposite sides, AB, DC, of any quadri- 

 lateral, A B C D, inscribed in it, the points of contact, P, Q, lie on 

 the line E G, joining G, the intersection of the diagonals, and E, the 

 inter.'iection of the other two sides of the quadrilateral. 



Let EG intersect AB, CD in H, K. Through H draw a line 

 jiarallel to C D, meeting the diagonals A C, B D in p, q, and the. 

 sides A D, B C in r, s. We have then the following equalities of 

 ratios :— 



CK H_s B_p DF Hr Hg 



DK°"H)"°H9 "^""^ CF"Hjj°"Hs 

 CK.DF Hs Up 



By multiplication, — 



DK.CP Hp H 



Hence, CK.DF = DK.CF, and 5_? 

 DK 



If M be the middle point of C D, then 

 M C - M K 



CP 

 DF 

 C K^ 

 DK" 



MF-MC 



may be >vritteii 



MC + MK 

 MC MP 

 llcnce, TTVi = rrH and M K . M F 



M F -H M C 

 =WC' 



