124 



SCIENTIFIC NEWS. 



[Aug io, iSS3. 



written out on a type-writer by a copyist who listens to 

 the graphophone. By means of the starting and stopping 

 key, which throws the driving wheel in and out of gear 

 with the recording cylinder, the message can be repro- 

 duced sentence by sentence, and reproduction stopped 

 between any two words, or in the middle of a word, if 

 desired. This enables the copyist to take from the gra- 

 phophone as many words as can be retained in mind, and 

 the machine waits while they are being printed on the 

 type-writer, or written out, as the case may be. Should 

 it be desired to repeat the message, a simple motion of 

 the hand, occupying only a second or two, places the re- 

 producer on any part of the record, and the latter can be 

 repeated a thousand times if desired. The graphophones 

 in general use are provided with treadle motors, which, 

 acting through a very sensitive regulator or governor, 

 gives to the record cylinder a perfectly uniform motion, 

 and as all machines are regulated to run at exactly 

 the same speed, a record made on one machine can be 

 reproduced correctly on any other. 



EXTINCT BRITISH BUTTERFLIES, 



And the Continuity of Existing Species by Means of 



Migration Considered. 

 '"PHE ordinary observer could not have failed to notice 

 the changes which have taken place in the fauna 

 and flora of the British Isles within, say, the last fifty 

 years. 



The plants and animals oi any country or district are 

 not absolutely identical for any two successive periods, 

 however brief. Some species are gaining ground, others 

 losing it, while yet others remain practically stationary. 

 These changes are perpetually going on, but very few 

 of them are placed on record. 



In the course of a few years the general changes 

 may be inappreciable to the ordinary observer; but 

 locally there are often considerable variations which can- 

 not fail to be detected on close scrutiny. These are 

 links in the great chain of changes whereby the fauna 

 and flora of one geological period are considerably modi- 

 fied, and are gradually converted into the fauna and 

 flora of the succeeding epoch. In the different groups 

 of animals and plants, however, these changes proceed 

 at markedly different rates. Some will change rapidly, 

 while in others the movement is scarcely perceptible. 



As a general rule, the change seems to be slowest 

 among the least specialized forms and among those 

 which have been established the longest — the most rapid 

 among the most specialized forms and such as have only 

 recently been introduced. 



The Rhopalocera, or butterflies of the British Isles, 

 have in particular undergone many great and important 

 changes, even comparatively within the last few years. 

 The lists of only fifty years ago are no longer trust- 

 worthy. 



We have records of many species occurring in this 

 country which are now extinct. Others, which were 

 very plentiful, are now only occasionally seen. Others, 

 again, which were widely distributed, have become very 

 local, and so reduced in numbers that we may safely 

 venture to predict that within a few years hence they will 

 be entirely extirpated, and the beautiful forms of many 

 which at present adorn our collections will be phantoms 

 of the past. 



On the other hand, there are very few species multi- 

 plying their numbers or widening their area of distribu- 



tion to compensate us for such losses. It is the nature 

 and extent of these changes which we are about to con- 

 sider. 



In order, however, to obtain an appreciable estimate 

 of the great changes which have taken place in our 

 Rhopalocera fauna it will be necessary to enter some- 

 what into details respecting the laws of their distribution. 



It is well known that islands are, as a rule, poorer in 

 species than a similar area on adjacent parts of the 

 nearest continent ; for instance, the number of species 

 of butterflies indigenous to the British Isles is only sixty, 

 while the number occurring in France is nearly four 

 times that number. 



This is brought about by the following means : the 

 isolation consequent on being separated from the con- 

 tinent precludes the possibility of many species passing 

 over from the latter to the island, and thus supplying 

 the place of those forms which may have become extinct, 

 from whatever cause, in the smaller and isolated area. 



Now, on a continent, if a certain species become ex- 

 tirpated in any limited district of similar extent the loss 

 would probably be only temporary ; for if it belong to 

 any of those species which are ever increasing their 

 area of distribution under favourable conditions, the 

 blank in question would be almost certain to be supplied 

 through migration, and the continuity of the species 

 maintained. 



Although the narrow strip of water separating us from 

 the Continent operates as an impassable barrier for many 

 species which would otherwise make their way over 

 here, there are some which possess a powerful flight 

 and are able to overcome the obstacle. 



In addition to our isolation, there are other important 

 factors which greatly assist in the reduction of our in- 

 digenous butterflies, and are really the primary causes. 

 Of these climate is, perhaps, the principal. Owing to 

 our proximity to the ocean and the gulf-stream, and 

 the excessive humidity consequent thereon, the number 

 of rainy days in the British Isles is greatly in excess of 

 that of any country on the Continent. 



Butterflies are entirely dependent on sunshine for 

 their existence ; and whereas we get so very little of the 

 requisite in this country, it will be seen that this is tend- 

 ing also to reduce the Rhofialocera-fauna of the British 

 Isles out of proportion to the latitude. 



The other important factor in the matter is increased 

 drainage and cultivation, thereby causing the extirpation 

 of many indigenous plants which constitute the pabulum 

 of certain butterflies the larvm of which are dependent 

 on them for food. 



All these causes operating together are, at the present 

 time, as they have undoubtedly done in the past, bring- 

 ing about the speedy extinction of our native butterflies. 

 What will be their ultimate fate we can only dimly sur- 

 mise. Only about a century ago the number of species 

 of butterflies inhabiting this country was probably half 

 as large again as at the present time. Many of the 

 species which have since become extinct have been 

 figured in various Natural Histories, and records of their 

 occurrence have fortunately been preserved for the use 

 of future generations. 



The most handsome species of all whose records have 

 been handed down to us is the scarce swallow-tail 

 (Papitio podalirius). It is only little more than half a 

 century since the last specimen was seen in this country — 

 namely, at Richmond Park in 1829. Judging from the 

 list of localities it used to frequent, it possessed a wide 



