April 6, 1888.] 



SCIENTIFIC NE^A/'S. 



331 



duced by throwing on a white screen the image of an 

 electric spark two or three inches in length, enlarged by 

 means of the lens of an optical lantern : forked lightning, 

 six or eight feet in length with its irregular zig-zag course 

 was most clearly demonstrated. After alluding to the 

 protecting power of lightning conductors, and their con- 

 struction. Dr. Marcet explained the formation of hail and 

 of waterspouts, and exhibited an instrument by Prof. 

 Colladon, of Geneva, for showing the formation of water- 

 spouts. He concluded his address with a few remarks 

 on the Aurora borealis and AustraUs the formation of 

 which was illustrated by de la Rive's experiment, which 

 consisted of successive discharges of electric sparks 

 through a partial vacuum while under the influence of 

 a powerful magnet ; electric sheets of light were seen 

 assuming the form of bands, and possessed of a certain 

 rotating motion. 



Mr. G. J. Symons, F.R.S., read a short communication 

 on " The Non-existence of Thunderbolts," and briefly 

 described the history of several so-called thunderbolts, 

 the specimens obtained being of an amusing character, 

 thus clearly showing that they were of a terrestrial and 

 not a celestial nature. 



READING LITERARY AND SCIENTIFIC SOCIETY. 



At a meeting held on March 13, the Rev. H. C. Lang, 

 M.D., F.L.S., gave a lecture on " Mimicry, as illustrated 

 by moths and butterflies." The chair was filled by Mr. 

 O. A. Shrubsole, F.G.S., who gave some illustrations of 

 mimicry from among the higher forms of animal life. 



According to the author the word " mimicry " is taken 

 to express a phenomenon in nature, or, rather, a law by 

 which certain animals imitate more or less closely other 

 natural objects or other species of animals for the pur- 

 pose of self-preservation. The principle of mimicry is 

 but a development of the great law of protective coloura- 

 tion. There is in all organic beings under the influence 

 of solar light, a tendency to the production of colour. But 

 it is an almost universal rule that each species of animal 

 has enemies in the shape of other species, which seek to 

 feed upon it ; or that it seeks itself to feed on other animals. 

 In the first case it has to escape its enemies or it cannot 

 long continue to live. In the second case the animal who 

 is in pursuit must also be concealed from his prey or he 

 will be seen ; his prey will seek concealment, and he will 

 be starved. But colour is in itself conspicuous and does 

 not tend to further concealment, hence the necessity for 

 " protective colouring." In some cases protective colour- 

 ing is unnecessary, as when an animal is protected in 

 other ways and does not need to be concealed. Sometimes 

 even bright colours are a protection, as when an animal 

 is poisonous or otherwise unfit for food. Protective colour- 

 ing is common among the vertebratse, but more so among 

 the invertebrate animals, particularly among the class of 

 insects, and in this class especially in the order lepidop- 

 tera, where bright colouring is frequent, and where the 

 species are preyed upon by a variety of enemies, such as 

 birds, reptiles, predacious insects of other orders, but 

 most of all by birds. There are two kinds of protective 

 mimicry : (i) Where the form or colour of other natural 

 objects is imitated, such as leaves, stones, moss, Hchen, 

 wood, etc. Instances were given and specimens of lepi- 

 doptera were exhibited to illustrate this. (2) Where 

 certain species of lepidoptera which would otherwise be 

 preyed upon by birds, escape destruction from their re- 



markable resemblance to other species of an uneatable or 

 poisonous kind. In tropical countries the butterflies of 

 the families Danaidce and Heliconidcc are highly distaste- 

 ful to birds on account of the fact that they exude an acrid 

 and strongly-scented fluid, and they are found in number- 

 less instances to be imitated by butterflies of totally 

 distinct families, which do not possess the protective 

 advantages of the others. Illustrations of a few striking 

 examples were demonstrated, among which may be 

 instanced the case oi Papilio Mcrope, an African butterfly, 

 the females of which, instead of resembling the males, 

 take different forms in imitation of various species of 

 Dandis. In South America the Heliconidce are found to 

 be extensively imitated by butterflies of the family 

 Pier idee. 



SOCIETY OF ANTIQUARIES OF SCOTLAND. 

 The second meeting of this society for the current 

 session was held in Edinburgh on the loth March, Mr. 

 Robert Herdman, R.S.A., vice-president, in the chair. 

 The first paper was entitled " The Archaeology of Light- 

 ing Appliances," by Mr. J. Romilly Allen, F.S.A.Scot. 

 After describing the essential parts of an oil-lamp, the 

 author proceeded to notice the different varieties of lamps 

 which had been in use (from the Roman time downwards) 

 in Britain, illustrating the subject by reference to the 

 analogous forms of lamps and varieties of contrivances 

 for promoting and regulating the combustion of the oil, 

 in open or closed lamps, in use in different parts of the 

 world. Referring to the open lamps of stone found in 

 the Brochs, he compared them with the modern stone 

 lamps of the Esquimaux and the Chukches, and in this 

 connection the medieval cresset stones used for lighting 

 the churches and cloisters were also described. The 

 classical closed lamp of terra-cotta and the Roman hang- 

 ing lamp of iron were next noticed, the latter being the 

 prototype of the Scottish crusie, so familiar to our fore- 

 fathers, but now becoming so rare that specimens are 

 only to be seen in museums. After describing the 

 various contrivances for supplying the oil to the wick, 

 for regulating the supply, for trimming and hanging the 

 lamp, and the various adaptations of the form of the lamp 

 according to its special purpose, as for household use, 

 or for lighting a workshop, a street, or a mine, he de- 

 scribed the other varieties of lighting appliances for tallow 

 or wax instead of oil. The old rush-holders, candlesticks, 

 snuft'ers, etc., were arranged in their order of develop- 

 ment, from the rudest and simplest to the most refined, 

 and the paper was illustrated by a series of more than 

 forty drawings, and a large selection of actual examples 

 taken from the museum. In the second paper Mr. 

 Gilbert Gowdie, treasurer of the society, dealt with the 

 same subject from a more special point of view, describ- 

 ing a number of varieties of the Scottish crusie, with re- 

 ference to examples in the museum, and illustrating the 

 methods of their manufacture and use, with particular 

 reference to Shetland, where it is somewhat remarkable 

 that the common oil-lamp of the same form as that used 

 throughout the rest of Scotland is not known by the 

 name " crusie," but by the old Norse name "collie," 

 the kola of the Sturlunga Saga and the Gisli Saga. Mr. 

 Findlay and Sir Arthur Mitchell exhibited a number of 

 examples of crusies from the Continent, and made some 

 remarks on the similarities of difterent specimens from 

 different countries. 



