244 



NATURE 



[July 14, 1887 



the better form, but added the important improvement of 

 separating the prisms and arranging them in segments." 

 Edinburgh, June 28. D. A. Stevenson. 



In addition to several errors into which Mr. Kenvvard, in his 

 third article on "Lighthouse Work," has fallen, he seems to 

 have overlooked the experiments made by Messrs. Stevenson, 

 in 1870, on parafhn as an illuminant for lighthouses, and which 

 were fully detailed in the Parliamentary Paper 318, Session 

 1871. Experiments had been made with some degree of success 

 with burners having one and two wicks, but all attempts to burn 

 paraffin efficiently in the large concentric- wick burners were 

 unsuccessful until Capt. Doty solved the problem. Unaware of 

 what had been done in France, Messrs. Stevenson, early in 

 1870, had been conducting a train of experiments on paraffin, 

 and bad reached important conclusions on the subject, and good 

 flames were got with the single and double Argand lamps, when 

 Capt. Doty submitted his burners to them. The Doty burners 

 were then subjected to crucial tests in Edinburgh, and also to 

 actual trial for a month in a first-order lighthouse. The con- 

 clusions Messrs. Stevenson then arrived at and reported to the 

 Scottish Lighthouse Board may be summarized as follows : 

 that paraffin as now manufactured, with a high flashing-point, 

 is safe and suitable as a lighthouse illuminant ; the flames of the 

 Doty burners are of great purity and intensity, and easily main- 

 tained at the standard height ; the lamp-glasses and lamps in use 

 for colza are equally suitable for paraffin ; the varying state of 

 the atmosphere does not affect the penetrability of the paraffin 

 light more than the colza light ; no structural alterations on the 

 existing apparatus are necessary ; the initial power of the lights 

 will be exalted from 10 per cent, in the four-wick burner to fully 

 100 per cent, in the single-wick burner ; and that the use in the 

 Scottish lighthouses of the new illuminant would effect an 

 annual saving of ;i^3478. These conclusions, which subsequent 

 experience has fully borne out, settled the relative merits of 

 paraffin and colza so far as British lighthouses were concerned ; 

 and the first four- wick paraffin burner ever permanently installed 

 in a lighthouse was at Pentland Skerries on February 15, 1871, 

 while Argand paraffin burners were in use at Pladda in December 

 1870, and at the catoptric lights of Great Castle Head in 

 December 1870, and at Flamborough Head in June 1872. 



With reference to Ailsa Craig the facts are that in 1878, 

 when Messrs. Stevenson were considering the problem of effect- 

 ively guarding the Fair Isle by fog-signals, they consulted 

 Prof. Holmes as to the feasibility of working the signals from a 

 central station and sending the compressed air through a long 

 length of piping, and he concurred with them regarding its 

 practicability, and stated that he had worked a signal in Canada 

 at a distance of half a mile. When Ailsa Craig came to be dealt 

 with, the Fair Isle scheme was reverted to, and Mr. Ingrey's 

 firm contracted to carry out the work in accordance with Messrs. 

 Stevenson's specification. The automatic appliances for secur- 

 ing the true periodicity of the siren blasts were designed by 

 Mr. Ingrey. 



In giving the history of gas-engines applied as a motive power 

 for actuating fog-signals, a most important advance in lighthouse 

 work, Mr. Kenward does not state that this was done on the 

 Clyde by Messrs. Stevenson in 1875, and that since then they 

 have introduced gas made from mineral oil for driving gas- 

 engines at Langness in i88o, at Ailsa Craig, and at the Clyde. 



D. A. Stevenson. 



84jGeorge Street, Edinburgh, July 4. 



The Use of Flowers by Birds. ' ' 



I HAVE just read in Nature of June 23 (p. 173) Mr. W. 

 White's letter, and should like, with your permission, to add a 

 few words on this subject. A quiet, leafy home has made me 

 well acquainted with the commoner birds, therefore I speak. In 

 the first place, with regard to the non-protective colour of the 

 laburnum blossoms, it must be remembered that the flowers 

 thus used have two other qualities that recommend them to the 

 nest-builders : flexibility and length. Everyone must have 

 noticed how sparrows and other birds steal anything long and 

 limp — pieces of string, &c. — when they are building. Only the 

 other day I caught a sparrow trying hard to untie a piece of 

 thick string with which the branch of a tree had been tied back, 



and it would have succeeded if I had not gone to the rescue. I 

 have had the ties of budded roses taken away by them also. I 

 have been told by a lady that she once lost a lace handkerchief 

 in a mysterious manner, which was at last discovered — through 

 a telescope — on a high tree, on the nest of a rook or daw. All 

 the flower-sprays mentioned were long and limp. I have seen 

 birds take those of the clematis also. 



But there can be no doubt that birds have a very keen sense 

 of the protectiveness of colour ; if you startle a blue tit it will 

 seek a high branch against the sky-blue, and brown, and 

 green ; a robin flits away to the brown shadow of a bush ; I 

 have even known a young robin, threatened by an elder (they 

 are great disciplinarians), take refuge near a reddish-brown 

 dress. 



A thrush is wonderfully clever almost ' as soon as it is fledged 

 in finding its own tints on some wall or tree-trunk, and making 

 believe to be a piece of it to such an extent that one may 

 approach quite close to it and it will remain absolutely motion- 

 less as long as one's eye is upon it ; but if the eye is removed, 

 even for a "twinkling," the bird will have hopped down noise- 

 lessly behind something before one can look again. 



With respect to the yellow flowers, may there not be some 

 quality attached to the colour that birds like, or find profitable ? 

 I have watched a thrush during a long hard frost, devour — not 

 merely pull to pieces, but eat voraciously — large bunches of 

 yellow crocuses. All the earlier bunches were eaten. When 

 the purple and white came out later it was still faithful to the 

 yellow, and never touched any other ; and so eager was it, that 

 when the blossoms were gone it would dig its beak down into 

 the buds and pull out the least bit of yellow that appeared. I 

 watched it from a window close above the bed, and there was 

 no possibility of making any mistake about it. The bird — a very 

 large one — took some again this year, but not many. It could 

 hardly be all for love of colour, though no doubt that is very 

 strong in birds as in children. Birds are very like children. 



The sparrows mentioned in my last note made two more 

 trials after I sent it — five in all ; and the last time their attempt 

 was nearly composed of white alyssum. After that they gave it 

 up, but I get a severe scolding from them sometimes if I go 

 near the place. They tried to build there last year, and I 

 removed two or three nests, but I allowed a thrush, that had 

 built below and brought forth a brood before I perceived it, to 

 remain. When they left, the sparrows immediately built on the 

 top of the forsaken thrush's nest. They seem to have drawn the 

 conclusion — rather hastily, but not irrationally — that that was a 

 safe place, and whether or not their thoughts took the shape of 

 words, they chattered over their work immensely. And I do not 

 know where the line can be drawn between words and exclama- 

 tions (the foundation-stones of language), nor between those and 

 the notes and cries of birds, which are much more numerous 

 and varied and distinctive of purpose than most people imagine, 

 especially those of the robin. The strangely human and canine 

 cries of a party of quarrelling sea-gulls are extremely expressive. 



It may be said that there is no progress, no addition to the 

 language of birds ; but I am not sure of that. Last winter, a 

 robin, accustomed to be fed at my window on bits of bacon, 

 invented a note by which it called me to feed it. It was quite 

 peculiar — hushed, short, and muttered, as it were. Its object 

 seemed to be to reach my ear and not that of rival birds. It 

 would take a few little bits — very few — when offered, look grate- 

 fully in my face, with its head on one side, and away, till it was 

 again hungry ; then — da capo. The same robin is hopping in and 

 out of the open window continually now, taking what it pleases 

 for itself and young of food set for it. jiS3»'" 



That birds should be subject, like ourselves, to the tyranny of 

 fashion seems not at all unlikely if one considers the nature of 

 that tyranny. The feeling that seems to oblige people to adopt, 

 notwithstanding their sense of beauty and fitness, fashions that 

 are positively monstrous, must have its roots low down in the 

 scale of Nature. It seems to be composed of a sense of asso- 

 ciation and a love of the accustomed — both very strong in 

 birds ; association, for instance, of wisdom and authority with a 

 wig, of the delightfulness of well-bred women with the extremely 

 undelightful outlines they contrive to give to their figures, &c., 

 &c. The pleasure that the accustomed gives is, I suppose, 

 that of rest. No doubt fashion may reign in the lower regions ; 

 may it not control, in a somewhat transient manner, the bee that 

 packs its load from the pollen of a particular flower, of one 

 colour and no other? J. M. H. 



Sidmouth, July 3. 



