Aug. 24, 1888.] 



SCIENTIFIC NEWS. 



173 



fire. This is only necessary for a few minutes, and the 

 fire afterwards takes care of itself, just sufficient oil be ng 

 automatically supplied to keep the steam pressure within 

 the limit which has been set. This arrangement prevents 

 waste of fuel, as the supply of oil to the fire-box is 

 always controlled by the amount of steam taken to work 

 the engine, the engine itself putting out its fire when no 

 steam is taken, and relighting it again. The average 

 quantity of oil used per horse-power per hour is said to 

 be about two quarts. The simplicity of construction and 

 the excellence of material used in this engine, with its 

 automatic water and fuel feed, well adapt it for all uses 

 where it is desired to dispense with the services of a 

 fireman or engineer, while its compact form renders it 

 especially available for use on small steam yacht 



year. Most of the species mentioned above were once 

 probably truly indigenous to this country, but adverse 

 climatic influences have done their work, and they are no 

 longer able to find here a permanent home. 



Only about fifty years ago five species of copper 

 butterflies belonging to the genus Polyommatus occurred 

 in this country, while now there is only one — namely, the 

 Small Copper ( Polyommatus phlceas). 



The Large Copper (Polyommatus dispar) used to 

 occur very abundantly in the counties of Norfolk, Suffolk, 

 Huntingdon, and Cambridge, and its extirpation in these 

 districts has been attributed by one author to the rapacity 

 and greediness of collectors, though far more probably 

 the drainage of the fens this insect used to frequent is 

 the real secret, its pabulum, the great water-dock (Rumcx 



pleasure boat?. It is also suitable for all stationary pur- 

 poses, as well as for marine work. 



EXTINCT BRITISH BUTTERFLIES, 



And the Continuity of Existing Species by Means 

 of Migration Considered. 



(Continued from p. 160.) 

 pHE other species mentioned, namely, Pieris daplidice, 

 Argynnis lathonia, and Lampides 6oe/«:fl,though single 

 specimens of each of these have, at different intervals, for a 

 long succession of years been taken on our southern and 

 south-eastern shores, they all seem incapable of breed- 

 ing here in a state of nature. A single instance is on 

 record of a female Pieris daplidice which was captured 

 near Dover, depositing some ova which were kept in 

 confinement and produced three imagines the following 



hydrolapathum) , being a marsh-loving plant and only able 

 to thrive in such situations. We may also mention that 

 this butterfly has been recorded in times gone by from 

 several midland localities in South Britain, and was 

 therefore once probably found over a very wide area 

 in this country. In addition to the Large Copper 

 (Polyommatus dispar), three allied species — namely, P. 

 chryseis, P. hippothoe, and P. virgaurcce — all used to occur 

 in this country. 



The former of these (P. chryseis) is recorded to have 

 been taken by that eminent entomologist Dr. Leach in 

 Epping Forest, for several successive seasons, in abun- 

 dance, and was also said to have been captured in Sussex. 



Polyommatus hippothoe was formerly found in Whittle- 

 sea Mere, in company with P. dispar, andalso, itissaid, in 

 Kent, while P. virgaurca used to be taken in Cambridge- 

 shire (the Isle of Ely) and in Huntingdonshire. 



Alas, all these beautiful insects are now extinct, and in 



