168 



HARDWICKE'S SCIEN CE - G S S IP. 



NOTICES TO CORRESPONDENTS. 



All communications relative to advertisements, post-office 

 orders, and orders for the supply of this Journal, should be 

 addressed to the Publishkr. All contributions, books, 

 and pamphlets for the EniTore should be sent to 192, 

 Piccadilly, London, W. To avoid disappointment, contri- 

 butions should not be received later than the 15th of each 

 month. No notice whatever can be taken of communica- 

 tions uhic/i do not contain the name and address of the 

 writer, not necessarily for publication, if desired to be with- 

 held. We do not undertake to answer any queries not 

 specially connected with Natural History, in accordance 

 with our acceptance of that term ; nor can we answer 

 queries which might be solved by the correspondent by an 

 ai^ieal to any elementary book on the subject. 



J. W. H. — The pretty flowers sent are those of the " Milk- 

 wort" {Polygala vulgaris), pink and blue varieties. 



F. G., Norwich.— Your query is difficult to answer, but on 

 the whole it is possible that the Chaffinch, having a more 

 general distribution, is more numerous than the House Spar- 

 row ; that is, taking- the country through. 



L. T. — You are quite right,— the moss is Pottia truncata. 

 F. C. — See last number of SciKNCK-Gosrfp, Dr. Knaggs's 

 artic'e on " Collecting and Preserving." The larvK in public 

 collections are preserved by professionals, who keep their 

 mode of working as secret as possible.— C. G. 15. 



H. M. J. H.— A first-class work on British Diptera (illus- 

 trated) is that by Mr. Francis Walker, F.L.S., published by- 

 Reeve, Covent Garden. 



A New Subscriber, Torquay.— Your query respecting 

 storm-glasses should have been sent to some publication 

 devoted to physical rather than to natural science ; but we 

 -will endeavour to answer it. The instruments usually sold 

 are closed at the top, and have a brass cap cemented over 

 them. We have made them of Eau-de-Cologne bottles, and 

 after filling, simply corking them. We never heard of any 

 opening being lelt ; in fact, if there were, the fluid would 

 quickly evaporate. They, as you are probably aware, are per- 

 fectly useless as indicators of the weather, and the crystalline 

 changes that take place are most probably due to changes of 

 temperature. If you push the cork a little way into the tube 

 and pour a little asphalt varnish on the top of it, you will 

 find it will seal up the opening effectually. 



H. G.WiSE. — We cannot without seeing the instrument 

 assign a reason for the imperfect illumination of the field in 

 your binocular. Try a piece of fine ground glass between the 

 object-slide and the condenser ; this will diffuse the light and 

 very materially add to the stereoscopic effect. Our instru- 

 ment performs well even with as high an objective as a J 

 when the ground glass has a strong pencil of light condensed 

 on the under surface. 



J. G.,jun., Londonderry. — Colloid Silica can be obtained 

 by dialysing a preparation of silicate of soda (which may be 

 procured at most chemists). This is decomposed by hydro- 

 chloric acid, and the liquid is placed in a dialyser, and the dia- 

 lyser placed in pure water. After the lapse of a short time the 

 crystalline material passes through it, leaving the colloid 

 si ica bclind. A di nyser resembles a little tambourine, and 

 is made of a ring of gutta-percha, over which is sti-etched 

 parchment-paprr (writing-paper will do). The dialyser is 

 floated in a vessel containing distilled water. — F. K. 

 DiATo.M. — We think A. would suit you best. 

 A Subscriber, Ashburton. — Immersion lenses are made 

 on a principle devised by Amici, which was adopted by Hart- 

 nach and Nachet of Paris, and several of the American 

 «)])ticians, but did not find favour here until the last few years, 

 when the advantages of objectives constructed on the immer- 

 sion principle began to be recognized. An immersion lens is 

 so called from tlie circumstance of a drop of water being 

 placed between the front lens and the object itself, on the thin 

 covering glass, so that the rays leaving it pass through a film 

 of vrater instead of air. It is well known that the loss of light 

 from the reflection of oblique rays from a surface of glass is 

 much less when they pass from water into glass than from air 

 Into glass. Immersion objectives require special corrections 

 for the purpose, and are useless if used as an ordinary dry 

 lens. Our leading opticians are therefore adapting an extra 

 front combination to the ordinary high power, by means of 

 which they can be used either as wet or dry lenses. Several 

 papers on the construction and advantages of immersion len- 

 ses will be found in the Munthly Mic. Jour. — F. K. 



H. H., Leeds.— The Water-beetle is Hydroporus depnssus, 

 recently out of pupa. Your specimens were smashed. They 

 ought to have been enclosed in a cork cell, or in a quill or 

 small box. 



J. S. D. — Instruments, &c., for egg-blowing may, we should 

 think, be obtained at any first class philosophical instrument 

 maker's, Sec. 



G. B. — The plant sent is Neottia nidns-avis. 



A. A. C. — We cannot tell what is the best fond for birds in 

 aviaries, unless we first know what kind of birds are kept. 



F. F. M.— Specimens mislaid. Numbers I and 2 are difficult 

 to determine. They are the midribs of sea- weeds ; but we 

 cannot tell the species. Number 3 is a zoophyte, Membruni- 

 pora pilosa. 



John Le Bas.— The specimens were not exuviae of fishes, 

 or anything organic. No organic remains whatever are found 

 in mica-schist. The specimens seem to us to be decomposed 

 felspar, with a proportion of iron. 



A Working Mav. — You had better ask us some definite 

 question in our " Notes and Queries," and you will have no 

 difficulty in obtaining an answer. 



Z. E. G.— Your mosses were named in last month's issue. 



J. C. K. — The specimens attached to the Clematis branch 

 are not cocoons, but the female of a species of Coccus, or 

 " Scale insect," which has been introduced into this country. 

 Like the Cochineal insect, the body of the female becomes the 

 shelter for the young, the mother dying to provide them 

 with this protection. The eggs may be seen underneath the 

 scale. 



Thomas Ro.mans.— The fungus on the leaves of Ragsvort 

 is an JEcidiuin. See Cooke's " Microscopic Fungi," coloured 

 illustrations. London : Hardwicke, 192, Piccadilly. 



Anony.mous — We beg to draw the attention of several of 

 our correspondents to our rule of not answering questions 

 unless accompanied by the real name and address. 



EXCHANGES. 



Notice.— Only one " Exchange'' can be inserted at a time 

 by the same individual. The maximum length (except for 

 correspondents not residing in Great Britain) is three lines. 

 Only olijects of Natural History permitted. Notices must be 

 legibly written, in full, as intended to be inserted. 



Strombus, Cyprrea, and other foreign shells, for British 

 Marine shells. — A. W. Langdon, Llanrvvst House, Hastings. 



Living Dytiscus or Co/ymbetes offered for slide of clean dia- 

 toms. — H. E. Freeman, 1, Rose Villas, Wood Green. 



For palate of Cyclostoma elegans send stamped and directed 

 envelope to J. H. Martin, 8(3, Week Street, Maidstone. 



Eggs of Red-footed Falcon, Grasshopper Warbler, Scoter, 

 Crested Grebe, Eared Grebe, Sclavoniaii Grebe, Pintail, Long- 

 tail, Scaup, and Eider Ducks, Sandwich Tern, &c.,for others. 

 T. H. Phuler, Vale Royal, Northwich, Cheshire. 



A vvell-.aiountei) Tongue of Bee, for Diatoms from Guano, 

 mounted and named.— H. B. Thomas, 13, Market-place, 

 Boston. 



, Will A, C. A., Post Office, Staines, kindly send a list of his 

 duplicate eggs to T. H. Phuler, Vale Royal, Northwich, 

 Cheshire } 



For F lustra foliacea send stamped directed envelope to P. 

 Smith, Legh Street, Warrington. 



For GempWariVi /or!c«/o/a send stamped envelope and ob- 

 ject to Miss E. de B. Meyrick, Downshire Lodge, Blessington, 

 Co. Wicklow, Ireland. 



CvcLOSTo.-MA elegans and Helix Pomatia in exchange for 

 other English shells, — B. F. Buxton, Easneye, Ware. 



For exchange or otherwise, an excellent English J-in, object- 

 glass of 120 degrees angular aperture, in perfect condition. — 

 Apply to the Rev. J. Bramhall, St. John's Vicarage, near 

 Lynn, Norfolk. 



Vallisneria, Frog-bit, Lemna frisulca, Drosera, Chelifers 

 or Petrobii, for marine or fossil diatom material. — J. G. R. 

 Powell, Matlock Bridge. 



BOOKS RECEIVED. 



" The Stone Age in New Jersey." By C. C. Abbott, M.D. 



'• Report of the Entomologicid Society of tlie Province of 

 Ontario " for 1871. 



"The American Naturalist," May. 



" Hypotheses." By F. J. Finois, 



"The Canadian Entomologist." No. 5. 



" Land and Water." 



" Les Mondes '' 



" The Insect World." By Louis Figuier. New Edition, 

 revised. London : Cassell, Petter, and Galpin. 



" Transactions of the Norfolk and Norwich Naturalist's 

 Society," 1871-72. 



Co.MMUNICATIONS RECEIVED FRO.M F. K. — F. P.— C. J. L. — 



J.H. G. (M.D.)-G. E. X.-T. S.— W. H, P.— T. L— S.A. B,— 

 W. E. S.-T. C. O.— W. H. G.— J. G, R. P.— J. B.— A. W. L. 

 —J. H. M.— H. E. F.— W. S.-T. H.P.— H.B.T.— E. D. 1!. M. 



— B. F. B.-R. H. A,— Dr. H. F. P.— J. R. D.-E. J. T.— 

 C. A. R.— E. W.— J. R. S. C— C. L. W.— R. H— J. G.— J. T. 



— H.-Dr. C. C. A.— J. D. L. T.— J. R. J.— F. B. B.— G. H. H. 

 — M. A, D.— C. A. R,— R. H. W.— J. H. C. C. S.— G. O. H.— 

 H. E. B. 



