KNOWLEDGE ♦ 



[Sept. i>2, 1882. 



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i?m 



Irttrrsf to tfjr Cliitor. 



[Tks EJito^ Jo^amotkotJ \\m»tl/rtfpf>n»%hte for tXt opinion* of kit correfponJent*. 

 S* f^mnct mmJertiikr to rfturu mttmMrripts or to corretpond leitk tketr irn7#r». Jll 

 cQmautm%€^imu »ko%U U lU tkort a* posfibtf, eonsitUntly icUk/ull tinJ cUar niatt* 



Mt SJUirrial commmmi<^'t\ont tkouJJ h* adJret»rd to tkt Editor of KltowLVDCB : 

 the Pmbtitkrr; at tke Offict, 74, Great Qufen- 



amj Foat-Offic* Ordera akould b« made payable to 



All JZ/.i/Zax-o, Ckt^M, 

 Jlm^> H-.-J. * So... 



',' All IfHm lo l\e Editor rill ht yumhrrrd. For « 

 LOtrttp o mdemtt, rken rf/errim<l to amy Itttgr^ trill obtifff by 

 amJ Ik* f^iye on rkitk it appt^ra. 



*' In koowledi:*, that mmn odIt if to hf contemned luid deipiwM who is not in ft 



•tftt« of trmatition ^'or ia thrro anvthiDg more adrene to accuntcy 



than flxilT of opinion." — Ftiraday. 



** Show' me a man who make* no mistakes, and I will show jou a man who has 

 done nothing."— Zt>&(y. 



SINGULAR RAINBOW. 



[5C2] — What J. R. Rountliwaite describes in Knowledge for 

 Aug. IS id a Tory rure siVlit, owing to two circomatanccs which he 

 appears not to have noted. When such a tertiary bow has been 

 «c«n before, there has been a sheet of water lying between tlie 

 obaerrer and the bow. and the sun has been at a low altitude. 

 M. Elicnne saw one at Chartres on Aug. 10, lUC5j and Halky, the 

 aatroDomer. saw a tertiary bow on Aug. 6, 1C98 j in both the cases 

 a river was between the observer and the bow, and the sun was only 

 about 6* above the horizon. Half-a-dozen such bows, or fragments 

 of them, have been seen during the last ten years, and in all there 

 has been a reflecting sheet of water and a low-lying sun. 



XV'\ 



Some ninety years ago a fragmentary quarternary bow was seen. 

 The obwr%-er was a Mr. Stnrge; the place Alverstoke, on the sea- 

 coast of Hampshire ; and the time evening, July 9, 1792, with the 

 ■an low in the horizon to the N.W. Portions of the primary and 

 secondary won- accompanied by fragments of tertiary and quartor- 

 nary bows, as in the accompanying diagram. I have dotted the 

 continnationn of these fragments to give an idea of what would 

 have been seen if the atmospheric conditions had been favourable. 

 Where the secondary and tertiary Ikiws overlap, there would have 

 lii-cn, as in the case of Hallcy's observation, a portion of a white 

 arch. William Ackbovd. 



MECHANICAL PARADOX. 

 [563] — The " learned pemon" with the dead language name, 

 who has made the inqniry about Ferguson's mechanical paradox, 

 will find the identical article itself in the museum collection of the 

 British Horological Institute, Northampton-square. It was made 

 to demonstrate the Unity of the Trinity. C. 6. M. 



HOT AND OLD DRINKS. 

 '50r — Sorely Mr. Allinson {TiM) is wrong in saying that "a 

 temperature of 100' Fahr. destroys p»-[>«in, and leads lo indi- 

 gestion." According to McKcndrick {" Physiology," p. 2.10, 

 ed. 1878). " the transformation of albumen into peptones" is only 



" arrested at 5° and GO" C, i.e., -tl" and 140° Fahr." Again, the 

 "rodneas" of tho stomach, which Mr. Allinson says follows the 

 imbibition of hot drinks, follows equrilly (Ams it not?) tho de- 

 glutition of a piece of bread. K. U. o. 



[oG3]— Mr. Allinson (53-1, p. 23."i) says that " a tcinperature of 

 UX)° F. also destrovs the active power of the gastrin juice — 

 (.opsin." This is a mistake— very likely tho printer's. 100° F. is 

 I lie normal temperature of tho stomach, and tho most favourable 

 for tho action of jiepsin, whether in the stomach or as fomid in 

 experiments on artificial digestion. Kirkos, in his " Handbook of 

 Physiology," says : " Pepsin probably acts tho part of a hydrolytic 

 ferment." Tlio characters of these ferments arc (page 201 ) : " This 

 action is quite prevented, or much retarded, by cold, a moderate 

 warmth (100° F.) greatly focilitates it, while a high toniperaturo 

 (above 140' F.) completely prevents this action." Ico-pudding 

 after a heavy dinner, and the American habit of drinking much 

 iced water, are often tho cause of indigestion. In tho matter of 

 drinks, as in most things, tho rule medio tutissimus holds good. 



M.D. 



SKELETON LEAVES. 



[56G] — A large saucepan of cold water, a piece of scrubbing sonp 

 about four inches square, cut into small slices. Gather viatnrc 

 leaves, seed-vessels, Ac. ; put some soaji into tho water, then a 

 layer of leaves one by one, then more soap, then leaves, and so on. 

 Put on a lid, set the pan by the side of a fire, and lot it simmer. 

 After an hour take out a few leaves, and try them between the 

 finger and thumb ; if tho pulp separates readily from tho fibre, 

 remove them from tho fire; if not, lot tho pan remain. Somo 

 leaves, such as ivy, orange, i-c., are done in an hour or two ; others 

 of a tougher fibre take half-a-day. Seed vessels of mallow or 

 campanula take a short time. Largo poppy or stramonium requires 

 perhni)8 two days. Now lay a loaf U])on a plate, under a taj) of 

 running water, and beat it with sharp strokes with a hard brush^ — 

 say a toothbrush ; the green matter will run oft with tho water. 

 When the skeleton is quite clean, dry it u))on blotting-paper. 



To bleach the specimeng put a quarter of a pound of chloride of 

 lime into a large bottle of water, cork it, and lot it stand somo 

 days. Strain it, and mix with more water in a basin ; immerse the 

 leaves, &c. Again carefully watch and remove them as soon as 

 they are white, for tho lime soon renders them brittle and rotten. 

 Wash again in pure water, and dry as before. As tho atoms usually 

 come away from most leaves, it is well to boil several stalks sepa- 

 rately, and after bleaching to mount the leaves by gUTiiming them 

 to the stems. E. C. N. 



BRAIN TROUBLES. 



[.IGT] I have had lately a good deal of reading to do in a 

 relatively small amount of time — more oxactly, I have boon " cram- 

 ming" for an examination. In this painful process, ono has to 

 tabulate facts, or make a pr6ci« of a paragraph either mentally or 

 on paper. To write out these tables, Ac, takes up more time than 

 I can spare, henco I have to do it mentally. Now the brain 

 trouble, if it can be so-called, comes in. In reading light literature, 

 as I generally do for a short timo before going to bod, I find myself 

 carrying on tho same jinfrid— tabulating facts or fictions of the 

 smallest importance, and, more annoying, referring back to previous 

 paragraphs to rofrt-sh my memory as to tho earlier parts of the 

 table. Tho same thing takes place when any conversation is going 

 on around me, and oven while walking about I find myself trying 

 to impress faces, even tho appearance of any of tho various objects 

 one meets, on my memory ; in caao any of tho same nature may 

 turn up in the examination. This is done involuntarily, and, 

 indeed, requires somo mental effort to overcome. It is interesting 

 OH an example of the force of habit — I don't know if wo should 

 call it "unconscious cerebration." It is a small trouble, but very 

 annoying. John JoI'K, M.D. 



A LUMINOUS SEA. 



[508] — Your extract from the Heienlific Amerirun on "A Lumi- 

 nous Shark " reminds mo of an interesting sight I onco had the 

 good fortune to witness, viz., a luminous sea. On Monday, Jan. 20, 

 1871, I wag abont 750 mil9s S. 78° E. from Achen Lighthouse, in 

 the Arabian Sea, and at 1.30 a.m. was called on 'dock to see tho 

 nbovcmcntioned phenomenon. 



Tho whol<^ sea to the horizon was as white as milk, being ono 

 unbroken expanse of jihosphorescont light, and presented to mo 

 what I should imagine a plain of snow in the Arctic regions would 

 resemble at night. Tho ship I was in at the timo was drawing 

 about 22 ft. of water — the suction-valve to the circulating pump of 



