Aug. 10, 1888.] 



SCIENTIFIC NEWS. 



J25 



f distribution in this country. The prior recorded dates 

 * of its capture are as follows : near Beverley, in York- 

 shire, in 1778 ; near Norwich in 1810 ; Berkshire, 1826; 

 Shropshire, 1807, and again in 1822 ; Cambridgeshire, 

 18 1 8 ; also in the New Forest, the Isle of Wight, and in 

 Bedfordshire. Though the species is now extinct in 

 the British Isles, it occurs in considerably higher lati- 

 tudes in adjacent parts of the Continent. Its extirpation 

 over here may probably be attributed to adverse climatic 

 influences, isolation, and increased cultivation combined. 

 It is highly probable that a near relative of the preceding, 

 our only remaining representative of the genus Papilio — 

 namely, Papilio machaon — will follow suit not many 

 years from hence ; for when Papilio podalirhis used to 

 occur in this country Papilio machaon roamed over the 

 whole of South Britain, being found as far north as Cum- 

 berland and Yorkshire, westward as far as Wales, and to 

 the Isle of Wight in the south. There is also a strong 

 probability of its having occurred in the south of Ireland. 

 Now, however, it is entirely restricted to the fenny dis- 

 tricts of Cambridgeshire, Huntingdon, and Norfolk, 

 and it is even here much less plentiful than formerly. 

 It seems very likely that living entomologists will hear 



Fig. 5. Fig. 6. 



of the last swallow-tail being taken in Cambridgeshire 

 and Huntingdon, as both these districts are being rapidly 

 drained and cultivated. Many places where the Papilio 

 7iiacliaonhe\d its court are now corn-fields. In Norfolk, how- 

 ever, we may hope to have its extirpation retarded. The 

 butterfly in this county has its head-quarters in the neigh- 

 bourhood of Horning, and the fens hereabouts, owing to 

 tidal influences, are incapable of being drained. Long, we 

 trust, for the sake of entomology, may this be the case. 



A more remarkable case than either of the preceding 

 is that of the Black-veined White (Aporia crataigi). 



This insect only about twenty years ago occurred in 

 great abundance in many localities in the south of Eng- 

 land. Dr. Newman speaks of having taken it near Leo- 

 minster in great numbers at rest on flowers of the 

 ox-eye daisy. Since then, strange to say, it has become 

 entirely extinct in this country, and various have been 

 the speculations respecting its sudden and mysterious 

 disappearance. This, in our opinion, is due principally 

 to a long succession of wet summers which have pre- 

 vented the insect performing the functions of oviposition. 



It is very strange that while this butterfly does not now 

 occur at all in this country, it is to be found in great 

 abundance on the adjacent parts of the Continent, 



especially in France, where it is said sometimes to cause 

 immense destruction in orchards. In many districts the 

 fate of the fruit crop entirely depends on the abundance 

 or scarcity of Aporia cralcegi. 



The principal districts in our own country which it once 

 frequented were Kent, Surrey, Hampshire, Dorsetshire, 

 and Middlesex in the south ; Worcestershire and Here- 

 fordshire in the west ; and Northamptonshire in the east. 

 In the intermediate localities it was comparatively scarce, 

 It was not found at all in the North of England, Scotland, 

 or Ireland, at least as far as existing records inform us. 

 {To be continued.) 



SIMPLE EXPERIMENTS IN 

 PHYSICS.-II. 



Cohesion. — A pretty illustration of cohesion. The 

 force which holds the molecules of matter together is 

 shown in fig. 5. In the bottom of a suitable vessel is 

 placed a few drops of olive oil, and into the vessel is 

 carefully poured a mixture of alcohol and water having 

 the same specific gravity as the oil. The oil will be de- 

 tached from the bottom of the vessel, and will, in con- 

 sequence of the cohesion of its particles, assume a 

 spherical form. Another method of performing this ex- 

 periment is to introduce the oil into the centre of the 



Fig. 7. Fig. 8. Fig. 9. 



body of dilute alcohol by means of a pipette. By care- 

 ful manipulation a large globule of oil may be introduced 

 in this way. Cohesion tends to cause liquids to assume a 

 spheroidal form, but in the case of liquids in large masses, 

 gravity causes them to assume the form of the vessel in 

 which they are contained. The tendency of liquids to 

 assume a spheroidal form is seen in the rain and dew- 

 drops, in liquids dropped from bottles, also in liquids 

 thrown in drops on surfaces which they do not moisten. 

 Water spattered upon a surface covered with lycopodium 

 is an example of this. 



Specific Gravity. — The difference in the specific gravity 

 of liquids is illustrated in a striking manner by the " vial 

 ot four liquids/' shown in fig. 6. A test-tube with a foot 

 makes a convenient receptacle for the liquids. In 

 the bottom of the tube is placed mercury. The 

 second liquid in order is a saturated solution of 

 carbonate of potash. The third is alcohol, coloured 

 with a little aniline red to mark the division 

 of the liquids more clearly. The fourth is kerosene oil. 

 When these liquids are shaken up they mix mechani- 

 cally, but when the tube is at rest the liquids quickly 

 arrange themselves in their original order. The egg ex- 

 periment shown in figs. 7, 8, and 9, although without 

 novelty, is interesting on account of its simplicity and 

 effectiveness. Two pint tumblers or similar vessels "are 



