April 7, 1882.] 



KNOWLEDGE * 



503 



np of the rock that is taken out in sinkins; the pits and driving the 

 roads, and most of tlic rocks — "the coal measures," as the miner 

 calls them — contain vegetable matter, the most characteristic being 

 the'linstay" or " linsoy" rocks, so named by the collier on account of 

 their resemblance to the striped " linstay " or " linsey " of which his 

 wife makes her petticoats. This rock consists of alternate bands of 

 black vegetable matter and of sandstone. The friable shales of the 

 coal measures are similarly interstratified. It is this vegetable matter 

 (in some cases increased by coal screenings) that fii-es on the pit 

 bank. The tendency to such combustion is increased by the 

 presence of iron jn'rites — a compound of iron and sulphur, both of 

 which are combustibles and do burn, or oxidise, readily when 

 exposed to air and moisture. Iron pyrites is especially liable to such 

 spontaneous combusti(»n, and is thereby converted from its gold-like 

 insoluble form into the readily-soluble ** green vitriol," or sulphate 

 of iron. This explains the sulphurous fumes to which " One who 

 wants knowledge " alludes. — W. JIattieu Willums. 



9[n5U)cij> to Coirrsfpontifnts. 



','All eommutiiciilioiit for the Edilar rrguirin^ f„rh atlf:ilion ihoiild reach the 

 Ue on or before the S,iliirdai, precejinn the cnrreiit'ifue of KxowLBDGB, the 



ircittation o/" tchich eompeU ui to go to prett early ift the u-eek. 

 HiSTS TO COKRESPOSDBSTS.— 1. J\"o qur.liont ii.trin^ for ncienlijic information 

 tan ie amicrred through the post. 2. Letters rent to the Editor fur corretpondentt 

 cannot be forwarded ; nor can the namet or addrenfen qf correnponderitt be given in 

 anever to private inguirief. 3. So queries or replies savouring of the nature of 

 advertisements can ht inserted. 4. Letters, queries, and replies are inserted, unless 

 contrary to Rule 3, free of ehartie. 6. Corrtspondeuts should rcrite on one side 

 •ii/y of the p-iper, and pat drarings on a separate leaj. 8. Each letter, query, or 

 reply should have a title, and in replying to letters or queries, reference should be 

 tiade to the number qf letter or query t the page on tphich it appears^ and its title. 



Laiiv Stkwart.- Regret very much that an advertiser in our 

 columns has been so dilatory (I trust that is the limit of his 

 offence). Your letter has been forwarded to the publishers, and 

 due measures will be taken. — Glaoiator. Fencing hardly a scientific 

 subject. As it chances to be a favourite exercise of mine, I will 

 give my own ideas about your diUicnlty. You ought, considering 

 the name you adopt, to be able readily to meet the im, deux, and 

 un, deux, tmis, which your opponent is so fond of using, in tlie 

 ordinarj- way. If I were you, I would not give in till I had acquired 

 the knack. But, if yon cannot, try what Mrs. Glasse would call "another 

 way." Follow him with the round parade. This will bring him up 

 in carte, instead of carte over the arm, and all he can do is to try 

 carce over the am again, which you can treat in the same way, 

 following up his blade. Remember, though, that this parade is not in 

 itself a defence. A good fencer will corkscrew in upon you, if you 

 forget this. The parade simply changes the direction of your guard. 

 Thus if you meet a thrust in carte over the arm with the round 

 parade, you are engaged in carte and innst defend accordingly, that 

 is towards the left, not towards the right, as in the simple parade 

 for that thrust. So if you oppose the parade to un. deux, &c., 

 you are s.ife enough during your opponent's extension, but a.s the 

 lunge is delivered the parade merges into defence in carte. The 

 advantage of the round parade is that you know exactly where 

 your opponent's blade will be when the thrust is delivered. — Priam. 

 You may be surprised to leani that many of the marks of parenthesis 

 you counted so carefully were added after the papers leere iti type, 

 because, on careful consideration, they seemed more suitable than 

 commas. Macaulay (whose name j'on misspell Macauly) used to 

 boast that he seldom used the semicolon (not the parenthesis.) 

 Whateh". who severely rebuked the improper use of the parenthesis, 

 used it more freely than most writers. In fact, every logical writer 

 must use them, to write clearly and correctly. If it were not 

 in very bad taste to comment on faults of style, I would point 

 out that your letter would be all the better (at any rate, much 

 more easily understood) if you had used the parenthesis more 

 freely. Take, for instance, this sentence : — "It has been 

 on my mind ever since the first number of Knowledge to call 

 attention (in a friendly way) to a small evil, on the part of the 

 editor himself, and (in degree) of some contributors, of the con- 

 stant use of the parenthesis in the articles." Here, I hare added 

 parentheses where they are obviously not merely necessary, but 

 essential to the grammatical accuracy of the sentence. Without 

 them, you might mean "a friendly way to a small evil," and 

 "in degree of some contributors." Yonr first sentence would 

 farther bo improved by the addition of a da.sh after "evil "and 

 "contributors," though,, even then, "a small evil of the constant 

 ase" would be hopelessly ungrammatical. In fine, my dear 

 BIT, every sentence of your letter suggests the repetition 

 in your case of a small quotation I hare already had to use 



in reference to correspondents wlio, having evidently had small 

 experience themselves, undertake to teach me how to do what 

 has been the business of my life. " Teach not a parent's parent, 

 I would beg of you, "to extract, the embryo juices of an egg 

 by suction ;" the good old lady can the feat enact q.-ite irrespective 

 of your kind instruction.— Akthlk Bvchukim. Do you make no dis- 

 tinction between the ordinary use of the term logarithm and its 

 use in the theory of functions'? Or, supposing you do draw such a 

 distinction, do you suppose our querist referred to the latter use ot 

 the term ? What you so carefully explain to mo is as familiar as 

 the interpretation "of imaginai-y expressions (of the imaginary cube 

 roots of unity, for instance). Of course, log {-a) has its meaning, 

 just as \/-a has ; but e<iually of course that meaning is outside the 

 ordinary use of the function", precisely as ^/- a means something 

 which cannot be defined in ordinaiy arithmetical or algebraical terms. 

 — R. W. R. Yes, that is a fair enough account of apparent planetary 

 motions.— J. Smith. Have never heard that telesco[nc work injured 

 the eyes appreciably. Galileo was certainly not blinded by ordinary 

 telescopic observation. Jlilton died blind, but that does not prove 

 that making poetry hurts the eyes.— William G. C. Yes, "the 

 subject has taken up space in Knowledge,"— scarcely a reason for 

 continuing the discussion.— H. Judge, T. G., E. C. K., A Constant 

 Reader of " Knowledge," J. H.uivey, Spoopendvke, and others. 

 Queries vague, trivial, or for other reasons unsuitable. In future, 

 questions relating to books on special subjects cannot be admitted, 

 though regular contributors on sudi .'subjects may indicate books 

 they consider suitable. Advantage has been taken of oar Query 

 column to ask questions and to answer them in such a way as to 

 advertise books.- OnDEis. The query escaped our attention or it 

 would not have been in.serted. Of curse, " Clubs are tramps' is the 

 only correct expression.— M. Sor. BiB. Aech. Third part shall appeai- 

 very soon.— Jos. Gainswood. The appearance in qnesticn has no 

 scientific interpretation, though several well-meaning (but rather 

 foolish) attempts liave been made to find one. The story seems to 

 have had its origin in astrological fancies.— Excelsior. Thanks. 

 Corrections made.— Cambrian. Yes ; all satellites were probably 

 formed that way, and their greater or less distances would indicatcy 

 greater or less antiquity.- Clake. Most readers kcow about Dean 

 Alford's book on the Queen's English. The other matter is veiy 

 aptly described by you as " no business " of a certain correspon- 

 dent's.— A. C. Day. Those combination systems have always 

 failed in the working.— Hint. Very likely I may. " I do not say" 

 I won't; "but Time, my Christian friend."— AlICE BoDlNGTON. 

 Thanks, but you will have noticed that Mr. Clodd is attending to 

 Fala^olithic Man. 



BIOLOGY. 



H. St. Maynaed asks for the name of any good work on ''Ants." 

 He should consult Sir John Lubbock's " .Scientific Lectures" (Mac- 

 millan), and also the "Transactions of the Linna;an Society," for 

 much original information respecting the habits of these insects. 

 The price of Lubbock's " Scientific Lectures " will be ascertained on 

 application to the publishers, Bedford-street, Covent-garden.— A. 

 PoNTWOOD asks how Huxley divides the two orders of birds {RaHtce 

 and Carinat'i:). This is a sample of a question, the answer to which 

 would simplv represent a chapter of the most technical details 

 of comparative anatomv. I advise "A. Pontwood " to consult 

 Huxley's " Yertebrata ; "" but I may add that the Ratitm (ostriches, 

 i-c.) a"re classified by the structure' of the wing and by the nature 

 of the haunch-bones. The Cariiiafe birds are divided into sub- 

 orders, primarily by the nature of the vomer-boue of the skull, 

 and by its relations to other bones (e.g., the maxillo-palatines). 

 Thus, the Dromtp.ognathm (Tinamous) have the vomer, Ac. 

 resembling the emus. The Hcl.izojuatha! have " the lateral 

 maxillo-palatines ununited in the middle lino, separated from 

 the vomer by a fissure, and with the vomer pointed in front " 

 —and so on. Unless "A. Pontwood" is prepared to enter 

 npon a study of comparative anatomy, he need not attempt 

 to understand the details concerning which he writes.— A,. J. C. W. 

 — Diet of Tortoises. Yegetable matters, especially lettuces and 

 the like; a little milk occasionally.— AQfARiUM. See Mr. Gosse's 

 book on the " Aquarium " (Van Voorst).— Newts. These amphibia 

 should be kept (if water newts) in clear water, with growing 

 plant-life, ajid with a di-y resting-place admitting of then- 

 leaving the water occasionally. Food, worms chiefly. They 

 arc common in ponds in the country, or may be found 

 beneath stones near water. See Bell's " British Reptiles."— 

 J. Hamson. 1. The human skeleton you speak of found in the cave 

 at Mcntone, and spoken of by Riviere (Paris, 1S73), was found m 

 March, 1872. The cave is called La Barma du Cavillon. No metal 

 nor any poli.shed flint was found associated with it. The skull was 

 dolichocephalic ; and the whole surroundings (as well as the teeth) 

 indicated a savage life. The skeleton is of Palteolithic age 



