140 



SCIENCE-GOSSIP. 



[JuiN-E 1, 1865. 



IQ 



MICEOSCOPY. 



Exotic Diatoms in British Localities.— The 

 discovery of isolatedvalves of exotic diatoms does not 

 prove thatthey everlived in these isles. I have myself 

 found (very sparingly) mixed with fresh-water forms 

 species hitherto only detected in guano. In a ga- 

 thering made from a small ditch, I found some frag- 

 ments and one perfect valve of Aulaeodiscus scabcr, 

 and also several valves of Triceratium alternans. No 

 doubt these forms had been washed out of the ad- 

 jacent fields, which had probably been manured with 

 Peruvian guano. I had not cleaned any guano for 

 manyyears. I have also occasionally observed marine 

 and brackish-water species in washings from moss. 

 In one gathering I detected a valve of Coseinodiscus 

 radiatus and several valves of Pleurosigma iEstuarii. 

 These must have been floating about in the air, and 

 then brought down by the rain. We may fairly 

 conclude that unless a species is found alive, and in 

 tolerable plenty, it is not a native of the locality in 

 which it is discovered, more particularly if the species 

 are exotic. Thus, Arachnoidiscus has no claim to a 

 British habitat. I believe oidy three valves have been 

 fou^id, one by M. de Brcbisen, in a gathering from 

 Ilfi'aeombe, and described in the Synopsis of British 

 BiatomacecB, and two more twelve years after, by 

 Mr. Archer. It is very desirable that all who make 

 Diatoms their study should, before adding a new 

 species to the large number already (audin many cases 

 imperfectly) described, have found it plentiful and 

 alive. To describe it correctly it must be examined 

 living as well as dead. If the material is in sufficient 

 quantit}', a portion may be well waslied with Liquor 

 ammonia?, and afterwards with distilled water. By 

 this means the stipes, or filaments, arc preserved ; 

 and if the specimen is heated on the slide, it may then 

 be mounted dry or in balsam (Aclinanthes longipes 

 and brevipcs arc beautiful objects prepared in this 

 way); a further portion may be acidized in the 

 usual manner, as it renders striation more distinct. — 

 Fred. Kittoii, Norivich, 



Guano, &c., in Exchange. — I shall be glad to 

 exchange Upper Peruvian guano, Bichmond earth. 

 Nova Scotia earth, or China sea-soundings, rich in 

 foraminifera, for any good foreign material contain- 

 ing diatomaccfc, or British gatherings of one species 

 o\\\\.— W.J.B. 



Scales on White Cabbage Buttehely. — Will 

 any of your correspondents kindly inform me on 

 what part of the white cabbage butterfly the elon- 

 gated and tufted scales are found which are used as 

 lest objects ? I have never been able to find such as 

 are described and figured by Quekett and others. — 

 ir. II. Reynolds. 



Webster's Condenser (p. 90) is now being manu- 

 factured by a London optician. (See advertisement.) 



GEOLOGY. 



Serpentine is used as a kind of marble. It is 

 a silicate of magnesia, coloured very richly by 

 metallic oxides, especially those of iron, nickel, and 

 chrome. One kind, obtained from Cornwall, where 

 the Lizard rock contains veins of extreme leauty, 

 is remarkable for its brilliant red and mottled colour 

 contrasted by veins of the purest white, and taking 

 a very high polish. It is well adapted for small 

 ornaments ; but when used for church work, such 

 as fonts, internal columns, &c., its appearance is 

 injured by its numerous veins and cracks. The po- 

 lish, though brilliant, does not stand exposure to 

 weather or damp air. The Italian serpentine {ophite) 

 is a different mineral, and far less brilliant, the rich 

 red tints being absent, and the colour generally 

 mottled dark green. It is used, however, for similar 

 purposes, and is of nearly the same value. It is 

 comparatively soft, and very easily worked. Irish 

 Connemara marble is a variety of serpentine, and is 

 a very beautiful material for columns, tables, altars, 

 and other decorative purposes. Its colour is much 

 paler than the Tuscan, which it otherwise resembles. 

 — Ansted's "Practical Geology." 



Education in Geology.— There is no greater 

 mistake in modern school tuition, and none so 

 general, as the neglect of the natural sciences ; and 

 yet there are few departments of knowledge to 

 which boys are more readily and earnestly attracted. 

 The majority are naturally observers and collectors — 

 as witness their little cabinets of birds' eggs, butter- 

 flies, and minerals ; and it only requires encourage- 

 ment and direction to make them reasoners and 

 reflectors. If it be an important point in education 

 to foster habits of observation and discrimination, 

 then assuredly there is no theme so admirably 

 adapted as the field of nature, and no section so 

 accessible at all seasons as that of geology. It is true 

 that the ordinary branches of tuition must ever 

 occupy the main share of the schoolboy's attention; 

 but there are intervals when natural history would 

 be a recreation, and in that recreation the otherwise 

 dormant mind might be first awakened to interest 

 and energy. Get the mind by all means aroused to 

 self-exertion ; let it once taste the pleasurable excite- 

 ment of knowing in one department, and the battle 

 is won. The desire for further knowledge increases 

 with the growth of that kuowledge and strengthens 

 with its strength. And even where such subjects as 

 geology form no part of the regular curriculum, a 

 day in the field or an afternoon in the museum might 

 be given as a reward for diligence and proficiency ia 

 other departments, and in this way a certain amount 

 of available information might be imparted Avithout 

 any attempt at formal instruction.— P^^i^tf'* "Geology 

 as a Branch of General Education." 



