62 



NATURE 



\_N0V. 2 2, 1877 



friends has assured ma that I was perfectly justified in my 

 statement on this point ; and it was by one of these, who was 

 present at the lecture in question, that I was informed of the 

 very explicit statement made on that occasion by Mr. Crookes 

 of the views he then held, which were universally understood in 

 their plain common-sense meaning, 

 November 20 William B, Carpenter 



Fluid Films 



With reference to Mr, Sedley Taylor's interesting note on 

 Fluid Films, allow me to say that if a drop of water, clinging to 

 the outside of a glass gobkt, be lightly dusted with lycopodium 

 powder, and a fiddle-bow be drawn across the edge of the glass, 

 the drop will exhibit vortices, rotating in opposite directions. 



Highgate, N., November 19 C. Tomlinson 



Tuckey and Stanley.— The Yallala Rapids on the 

 Congo 



Capt. Tuckey is dead and goKe and cannot answer for him- 

 self ; it may therefore, perhaps, serve to clear his memory in some 

 measure of a doubt about the correctness of his description of 

 the Yallala Rapids in 1816, arising from the very different 

 account of them given by Stanley sixty years afterwards, if I 

 mention one of several facts in connection with American rivers. 



The late Sir J. Franklin, in his first and disastrous overland 

 journey to the Arctic Sea in 1821, describes the " Bloody Fall" 

 on the Coppermine River as "a shelving cascade about three 

 hundred yards in length, having a descent of ten or fifteen feet." 



Betwetn 1848 and 1851 this "fall" was visited five times ; on 

 one or other of such occasions the water was either at high spring 

 flood, at low summer level, or at an intermediate elevation, yet 

 under none of these conditions was the "fall" found to be more 

 than thirty yaj'ds long, if so much, the height being about fifteen 

 leet. 



Franklin and the officers with him were most careful and cor- 

 rect observers, so that I can only attribute this wonderful change 

 (from three hundred yards long to thirty) in the form of the cas- 

 cade to the wearing away of the material forming the bed of the 

 river, by the action of the water, assisted in a great measure by 

 the large masses of ice and the stones carried down with it during 

 the breaking up of the navigation in the course of thirty seasons, 

 only half the interval of time between Tuckey's and Stanley's 

 .visits to the Congo. 



Supposing a somewhat similar attrition, but in a less rapid 

 manner, to have been going on at the Yallala Rapid, the 

 description given by the former as he saw it may be equally 

 correct as that of the latter when he visited it in its altered shape 

 In 1877. 



May I add that a cataract may become a fall or a series of 

 falls, and vice versd, according as the water in a river is in flood 

 or at low level. J. Rae 



Scientific Club, November 16 



The Future of our British Flora 



It may interest Mr. Shaw to know that the stations given by 

 Lightfoot in his " Flora Scotica, 1777," still exist (as far as I am 

 aware, and I have visited by far the greater number of them) at 

 the present day. Experience has led me to the conclusion that 

 a plant however maltreated, does not become extinct unless the 

 natural cottdiiions are changed, as by the draining of a marsh, 

 &c. I have over and over again found plants in stations where 

 they were reported as "extinct years ago." Perhaps if Mr. 

 Shaw visits his station for the " Lizard Orchis " (is this Orchis 

 hircina, L. ? if so it is, I fancy, new to Scotch botanists) in the 

 course of a year or two he may find it in as large quantity as ever. 

 As regards the maltreatment of plants, I agree with what Mr. 

 Shaw says respecting professors of botany. Each teacher of the 

 science ought to teach his students that it is a crime to extermi- 

 nate a plant, and that they can best learn botany from the 

 observation of the common plants of their district ; there is great 

 room for improvement in this respect. 



While a s udent I was often disgusted by seeing rare plants 

 torn up and then cast away as if they had" been a handful of 

 grass, or, worse still, put in the vasculum and forgotten till the 

 next Saturday, when they were" thrown away ; and all this without 

 a word of remonstrance from those who ought to have exercised 



authority, "that's villainous, and shows a most pitiful ambition 

 in the man who uses it." 



Provided we reform a little, I do not think that, judging of 

 the future by the past we have any reason to expect a large 

 decrease in the ranks of our native flora. I do not supposa any 

 species given by Lightfoot 100 years ago has become extinct even 

 in his stations, and on the other hand we have had a consider- 

 able number added to it since his time. 



Edinburgh A. Craig-Christie 



Selective Discrimination of Insects 



In continuation of the interesting observations of " S. B."" on 

 selective discrimination of insects in Nature, vol. xvi. p. 522, 

 permit me to send you the following notes from my journal, 

 made in August last : — 



•* Watched by the roadside near Kew Bridge Station, several 

 species of Hymsnoptera, of the genus Bumbus principally ; one 

 visited thirty flowers of Lamiun purpiircum in succession, 

 passing over without "notice all the other plants in flower on the 

 same bank — species of Convolvulus, Rubus, Solanuvi. Two other 

 species of Bombus and a Pierisrapa; also patronised i\iQ Lamium, 

 seeking it out deep in the thicket, thrusting their probosces even 

 into withered cups, although the Rubus' flowers were far, more 

 accessible and seemed much more attractive, being fresh and 

 well-expanded. 



" On the same bankseveral species of Diptera — »S)7-//«« chiefly 

 — were visiting the Rubus, ignoring the Lamitcm. On another 

 bank, some distance removed from t'ae first, I observed, how- 

 ever, that the diptera were visiting the Latnium (one species 

 was very busy on the convolvulus, applying its proboscis to the 

 external aspect of the anther) while the Hymenoptera, species 

 of wasp, were giving their attention to the Rtibus.'' 



I am sorry not to be in a position to identify the species of 

 Hymenoptera and Diptera, being unable to capture specimens of 

 either. Henry O. Forbes 



Highgate, N. 



The Earth-worm in Relation to the Fertility of the Soil 



In your number of the 8th instant there are some interesting 

 remarks upon the habits, &c., of the common earth-wnrm. 

 From frequent observations I fully concur with the remark that 

 the worm does not consume living vegetation but only vegetable 

 matter undergoing decomposition. 



I am also rather inclined to the opinion that there are (or may 

 be) two reasons for the drawing in to their holes dead leaves, 

 &c. , the one being, for use as food, and the other to protect the 

 holes from a too plentiful supply of water. 



In this same connection I may mention what I have not before 

 seen mention of, namely, the little mounds of small gravel stones 

 which the worms heap up around the entrance to their holes. 

 These are very curious and may be partly to prevent the entrance 

 of water ; and also, as I think, partly for rubbing against the 

 worm's slimy body, as fish do. 



It is very remarkable the extent to which loose gravel-stones 

 (some as large as a hazel-nut, and even larger) are removed from 

 a gravel-walk from distances quite beyond a foot, leaving the 

 walk pitted all over. I have never seen a worm in the act of 

 moving these stones and it is difficult to imagine how it is done, 

 but as it generally takes place in wet weather, it may probably 

 be by an adhesion of the stone to the slimy body of the worm. 



As regards fertilising eff'ects, it would be interesting to know 

 whether the earthy matter composing worm-casts had passed 

 through the worm's body, as the writer supposes, for in that.case it 

 would probably have more fertilising properties than if consisting 

 merely of the natural soil thrown up as by moles. 



The remark by one of your correspondents as to his observation 

 of a line of darker soil thrown up by worms from a substratum of 

 ashes deposited a considerable time before, would almost make 

 it appear that the molc-like action above referred to took place. 

 The writer, however, repeats his conviction that the matter 

 composing worm-casts has passed through its (the worm's) body- 



31, Stockwell Park Road Geo, H. Phipps 



Smell and Hearing in Moths 



"J, C," seems to draw inferences that moths have not the 

 power of smell but have that of hearing. I feel quite certain 

 they possess the former, but am in doubt about the latter. For 

 the purpose of catching moths I use a preparation of beer and 



