204 



KNOWLEDGE 



[NOX'EMBER 1, 1892. 



for many years before in favour of waste. TLe glacier of 

 Argentieres has been observed to have increased during 

 the last few years in length, height, and width. The 

 Mer de Glace is recovering some of its lost ground and, 

 one may add, scroe of its lost beauty ; the glacier de 

 BosEons is advancing and overturning many of the sapling 

 spruces which, in the period of its retreat, have im- 

 prudently ventured to grow on its moraines ; and the like 

 phenomena have been observed in other parts of the Alps. 



As regards the outburst of water from the glaciers, it 

 may be worth while to mention an event of the same 

 l;ind, though on a much smaller scale, which has since 

 occurred on another flank of Mont Blanc. On the eastern 

 side of the glacier de Bossons, high up and very nearly 

 under the Pierre Pointue, a stream flows from the glacier 

 and rushes down the mountain side in a wide channel, of 

 which in ordinary times it occupies only a small part. 

 About ten o'clock in the morning of the 11th August a 

 sudden outburst of water took place at this spot, and 

 rushed as a muddy torrent down the water-course, carrying 

 with it great stones, masses of ice and trees, destroying 

 the bridge which crossed the stream, and at one spot 

 breaking over the high bed of the stream and finding a 

 new course for itself through the forest. At the time I 

 was going up the Brevent and I heard the great roar of the 

 torrent, and some of my party saw it descend. The next 

 day I visited the spot where it had flowed over the bank, 

 and found the forest there strewn with trees, torn up or 

 snapped off, with blocks of stones of cubic dimensions to 

 be measured by feet or yards, with blocks of ice and a 

 layer of mud and sand. Many trees which had withstood 

 the onset of the flood bad been stripped of every twig, 

 every leaf, and every particle of bark. On the trees which 

 stood on the high bank above the stream, the flood had 

 left a coating of mud as high as I could reach. 



Both the St. Gervais outbreak of water and this on the 

 glacier de Bossons occurred belore the greatest heat of the 

 summer that has just passed had set in. 



It has been suggested that a part of the water which 

 came down upon St. Gervais may have been due to the 

 mass of ice forming a dam and so accumulating the water 

 of a stream till it rose to such a volume as to burst through 

 the dam. But the facts, so far as I can gather them, do 

 not favour this suggestion. No one appears to have seen 

 such a dam, or to have seen any trace of it after the 

 event. No stream would seem likely to have been so 

 dammed except that from the Bionnassay glacier. There 

 se?ms to be no doubt but that the chalet near the foot 

 of the glacier was destroyed on the same night as the 

 baths of St. Gervais. 



I am indebted to Monsieur J. Tairraz for permission to 

 use, for the purpose of the engravings which illustrate 

 this paper, some of the very interesting series of photo- 

 graphs illustrative of the event which were taken by him, 

 and which are well worth the attention of all who are 

 interested in such matters. I am further indebted to him 

 for a great dual of information most freely and clearly 

 communicated both by word of mouth and by letter. 



CATERPILLARS.- 



By E. A. Butler. 



I. 



BY their frequently attractive colours, the ease with 

 which most of them may be reared, the startling 

 nature of the changes they undergo, and the 

 great beauty of the resulting perfect insects, the 

 larva^ of Lepidoptera ha^e long since made them- 

 selves general favourites. Childhood's first essays in the 



direction of practical natural history often consist, to the 

 more or less serious detriment of the comfort of the house- 

 hold, and the neglect of nursery proprieties, of the pastime 

 of "keeping caterpillars," while the zealous work of man- 

 hood's maturer years may be given, as ui the case of the 

 late Mr. Buckler, to the delineation of their forms and 

 the unravelling of their life-history. They . sometimes 

 force themselves unpleasantly on the notice of the com- 

 munity by the violence they do to agricultural interests or 

 to sesthetic sensibilities, when they multiply to such an 

 extent as to cause either great destruction or at least un- 

 sightly disfigurement of cherished objects of culture in the 

 field or garden. They have sometimes proved so great a pest 

 as to have earned for themselves a place in the records of 

 history, and their name has become proverbial as that of 

 a national scourge. In the days of mediaeval superstition, 

 when the animal creation was supposed to have its duties 

 and responsibilities to humanity as well as humanity to it, 

 caterpillars, along with other destructive creatures, were 

 made the subjects of lawsuits and cited as defendants in 

 the civil and ecclesiastical courts, where the penalties of 

 the law were solemnly pronounced against them, and the 

 curses of the Church and the terrors of excommimication 

 held over them if they did not leave the district within a 

 specified time. At such trials the accused were not 

 always represented by proxy, but were .sometimes caused 

 to appear in their own persons before the judges ; thus iu 

 1451, during a plague of leeches in Switzerland, the 

 Bishop of Lausanne suggested the advisability of procuring 

 some of the aquatic worms and placing them before the 

 magistrates. This was done, and they were ordered to 

 leave the district in three days on pain of falling under 

 the ban of the Church ! In more modern days, on the 

 other hand, caterpillars have become the handmaids of 

 science by reason of their ready adaptability to observation 

 and experiment ; not only has their anatomy been duly 

 investigated, but in connection with their peculiarities of 

 form, colour, and markings, they have formed, and are 

 still forming, the subjects of researches which may be 

 expected to throw much light on several fascinating bio- 

 logical questions. If it be asked, for instance, why cater- 

 pillars are coloured and shaped as they are, it is not 

 nowadays considered a sufficient reply to say that Nature 

 is prodigal of beauty, but even the minutest peculiarities 

 of marking and form are eagerly scrutinized and compared, 

 in the hope of discovering tacts bearing upon the pedigree 

 of the creatures, or the influence of their environment 

 upon them. 



A caterpillar's life is not a very eventful one. The daily 

 programme is rather monotonous, consisting of alternations 

 of eating and ceasing to eat, and as a provident mother 

 has usually placed it in such a position that it is from its 

 earliest hours surrounded with abundance of food of the 

 proper sort, there is little call for the exercise of any 

 superior intelligence in satisfying the somewhat imperious 

 demands of the periodically recurring hunger. But un- 

 eventful though on the whole it is, there are moments of 

 excitement which cause its long thin-walled heart to beat 

 more rapidly beneath its back, and its watery-looking 

 blood to course through its body with greater vigour than 

 usual. There is first, for e.xample, the act of hatching. 

 The walls of the often prettily ornamented little eggshell 

 are nibbled through, and a big-headed but otherwise 

 rather worm-like creature issues from the opening, pre- 

 pared to make an immediate onslaught on the jn-ovisions 

 in its neighbourhood. The amount of eggshell eaten in 

 accomplishing this deliverance varies in difi'erent cases, 

 the caterpillar being sometimes satisfied with making a hole 

 just big enough to escape through ; but, on the other hand, 



