126 
Proceedings of the P^oyal Society of Edinburgh. [Sess. 
or branch to another. Cock-birds crowed or screeched — so noisily that 
their voices could be heard to a distance of a mile, and in one case 
of 1| miles. 
The most interesting observations are those which refer to the time- 
relations of the beginning of the pheasant-crowing and the arrival of 
the sound-waves. In the inner area, pheasants were disturbed immediately 
after the sound was heard at Mountnessing near Brentwood (18 miles), 
Stevenage (30 miles), and Bradenham near High Wycombe (37 J miles) ; and 
before at Woodhall Park near Hertford (24 miles). In the outer area, 
the birds were disturbed before the reports were heard in 19 places, and 
after in 2, namely, Hunstanton and South Walsham (near Norwich), in 
or near both of which places the disturbance was also noticed before the 
sounds. The evidence from the inner area is thus not altogether in 
agreement with that of shaken windows, but the latter would be observed 
with the greater precision. There can be little doubt, I think, that the 
sound-waves preceded the air- waves within a few miles of the source, but 
that, near the boundary of the inner area and all over the outer area, the 
air-waves preceded the sound-waves. 
Miscellaneous Evidence . — Other evidence of the passage of the air- waves 
may be worth recording. At Turnham Green (13J miles) a lady, who was 
out-of-doors, held a powder-box open in her hand. Though the air was still, 
a little puff of powder rose from the box long enough before the report 
arrived for her to feel surprise. Blinds or curtains were driven inwards, 
several inches as a rule, at New Southgate (7 miles), Enfield (11| miles), 
Wimbledon (13 miles), North Cheam (14 miles), Twickenham (17J miles), and 
Sunninghill (21 1 miles). Observers in the open air noticed the swishing of 
tree-tops at Windsor (28 miles) and Ascot (31| miles), both places being 
close to the western boundary of the inner sound-area. At Windsor, it 
should be mentioned, the movement of the trees is said to have occurred after 
the sound was heard. At Aylsliam in Norfolk (103 miles) a somewhat 
similar observation was made ; but the wind was strong at the time in the 
eastern part of the county, and I do not feel confident that the movement 
was due to the inaudible air- waves. 
Air-Waves in the Silent Zone . — As shown in fig. 3, there are 16 places 
in the silent zone (including Ipswich) at which windows were shaken or 
pheasants disturbed. Windows were shaken at Biggleswade, Chatteris 
(Cambridgeshire), Bury St Edmunds, Ufford (near Ipswich), Ipswich, and 
Chelmsford, and were shaken violently, though there was no wind at the 
time, at Thrapston and Dunton (near Biggleswade). Pheasants crowed or 
screeched at Groby (near Leicester), Uppingham, Stamford, Holme (near 
