440 Mr. E. Blyth on the Genus Pyrrhula. 
caused by the action of the sea and weather on the soft sub¬ 
stratum, thus bringing into effect the law of gravitation. No 
doubt the island will continue to diminish, until at length it 
will disappear beneath the waves from which it sprung,—the 
fate of an adjacent island now covered with 15 feet of water, and 
known to the fishermen as the “ sunken Filfla.” On Filfla is 
found a tolerable supply of water, slightly brackish, but suffi¬ 
ciently sweet to be eagerly sought after by the thirsty fishermen, 
who resort there in the heat of the day to take their siesta. 
The w 7 ater trickles from the side of the rock, and in one place is 
collected in a large earthenware basin left by the fishermen for 
this purpose under the shade of a reclining rock, where even in 
the height of summer it issues cool and limpid. The reason of 
this is evident. The water is absorbed in the rainy season by 
the superlying limestone, and permeates slowly through it, as if 
through a dripstone, until it comes upon the impervious clay, 
when it is turned off in a horizontal direction. A thick stalac- 
titic crust has formed on the face of the rock, rising to the 
height of many feet. An enthusiastic collector of natural 
curiosities of my acquaintance was once nearly paying dear for 
attempting to gratify his wish of carrying away a piece of this 
incrustation. Applying his geologist's hammer to it, an immense 
slab of stalactite was dislodged at the blow. Fortunately, he was 
enabled by a rapid and vigorous leap to escape being crushed by 
the falling mass. A corresponding depression to that of Filfla, 
but to a still greater depth in some places, has occurred on the 
Maltese coast opposite. This downthrow may be traced for 
several miles along the line of coast, and serves to show the 
connexion that doubtless once existed between the mainland and 
the outlying Filfla rock. 
XXXIV .—Note on the Genus Pyrrhula. 
By Edward Blyth, C.M.Z.S., &c. 
(Plate X.) 
Until a comparatively recent period but one species of the 
genus Pyrrhula } as it is now generally accepted, was recognized 
by ornithologists. The Japanese race was not considered worthy 
