176 Proceedings of the Royal Physical Society. 



niesozoic and tertiary series of strata, where pervious strata, 

 capped by those which were impervious, have an area of 

 many miles in extent. The lower greensand, for instance, 

 which surrounds the London basin, is capable of absorbing 

 daily the enormous quantity of 146,000,000 gallons of water, 

 and this bed alone has a subterranean area estimated at 4600 

 square miles. Mr Prestwick assumes the thickness of this 

 bed to be 200 feet, so that the whole capacity of the subter- 

 ranean water-bearing mass will be equal to 920,000 square 

 miles, one foot thick. The hydraulic forces resulting from 

 the pressure of the overcapping strata on this bed, which is 

 virtually a water reservoir, will act in two directions, and 

 the pressure will be equal. A force will unitedly press from 

 either side of the basin ; and the most powerful strain of 

 both will be on the centre of the basin. It is certainly, 

 then, somewhat curious that a fault generally should be 

 found in the centre of these jurassic and tertiary basins ; 

 and that the course of a river should generally be in the line 

 of this fault. Add to this the fact, that borings for artesian 

 wells are generally successful only within twenty metres of 

 the river, and there appear to be sufficient data to excite 

 the inquiry whether such hydraulic pressure, as no doubt 

 actually exists in the strata, may not have been the proxi- 

 mate cause of these faults. 



III. Ornithological Notes. [With exhibition of Specimen is.) 1. Anthro- 

 poides virgo (Nuraidian Crane) ; 2. Syrrhaptes paradoxus (Pallas 1 

 Sand- Grouse) ; 3. Falco subbuteo (Hobby) ; 4. Pernis apivorus 

 (Honey Buzzard) ; 5. Bomby cilia garrula (Bohemian Waxwing) ; 6. 

 Botaurus stellaris (Common Bittern) ; 7- Botaurus lentiginosus 

 ( American Bittern) ; 8. Mergulus melanoleucos (Rotche or Little 

 Auk); 9. Circus cyaneus (Hen Harrier); 10. Parus cristatus 

 (Crested Titmouse) ; 11. Loxia curvirostra (Common Crossbill) ; 

 12. Alauda arvensis (Sky- Lark — a black variety) ; 13. Phalaropus 

 lobatus (Grey Phalarope). By John Alex. Smith, M.D. 



Since the close of last session some of our rarer birds 

 have been captured in different parts of the country. I shall 

 refer to several which have come under my own immediate 

 notice, taking them principally in the order of their oc- 

 currence : — 



