OF THE 20TH OF NOVEMBER, 1887. 
55 
(3) Apparent direction from which the disturbance reached various 
localities. 
It is naturally difficult to obtain trustworthy information as to 
the course taken by sound-waves radiating from a point high in the 
atmosphere. There are several causes which may operate to vitiate 
any exact conclusion as to the direction from which a sound so 
originating reaches the observer, apart from the general difficulty of 
distinguishing the direction of a sound incidental to the imperfec¬ 
tion of our organs of hearing. The sound-wave, too, may pass 
through several distinct strata of air before it reaches the earth ; in 
each stratum the conditions in respect to humidity, and otherwise, 
may be different; in each there may be a movement in a different 
direction, and of different velocity ; the sound-waves may thus 
become subject to a certain amount of deflection and change of 
character. They may also, it appears, lose in force.* These 
possible influences cannot be altogether disregarded in the case of 
an explosion taking place at a great height iu the atmosphere, and 
may perhaps be of greater importance in the case of a series of 
explosions, either at various altitudes, or approximately in the 
same plane of altitude. So also they may come into play when a 
sound is created by the rush of a solid body passing with extra¬ 
ordinary velocity through the air. Then again the waves may be 
modified, deflected, or echoed by the configuration of the surface of 
the earth, or by objects upon it. There seems a good deal of 
evidence of various effects arising from such causes in the preceding 
letters and other communications. 
The position of the observer will necessarily affect his power to 
estimate the direction of the sound. Clearly, observations from 
within buildings are of little value, except where a wave of air 
appears to strike one side of a house, or windows facing in one 
direction alone. There is also a natural tendency to associate vague 
sounds with some expected event, to which such a sound is, or may 
be thought to be, appropriate. Of this again there are a number of 
examples in the reports; some observers associating the sounds 
noticed with an explosion in London, and others with such local 
events as the passage of a train over a bridge, and similar causes. 
In spite of these difficulties, it is well worth while examining the 
reports which have been received bearing upon the direction from 
which the sounds and shock occasioned by the meteorite appeared 
to reach observers in different districts. Without going into 
elaborate detail here, it will be enough to point out the general 
results. 
In a district to the eastward of the meridian of Bedford 
* In the article “Thunderstorm” in the ‘Encyclopaedia Britannica,’ by 
Professor Tait of Edinburgh, it is stated, in explanation of “ summer lightning,” 
that when that phenomenon is due, as it often is, to a thunderstorm in the higher 
strata of the atmosphere overhead, “the reason why we hear no thunder” is 
“ not so much the distance from the spectator as the fact that sounds generated 
in rarer air lose rapidly in intensity as they are propagated into denser air.”— 
‘Encyclopaedia Britannica,’ 9th ed., vol. xxiii (1888), p. 330. 
