502 ON ATTRACTION CAUSED BY VIBRATIONS OF THE AIR. 
by Guardians, which arrangements are then approved or 
disapproved by the Poor Law Board. 
“ This division of duties cannot but tend to delay and to 
non-efficiency, and though your committee do not pretend 
to decide to which of these departments the duty of admi- 
nistering the law should be intrusted, they do not think such 
duty should be shared between two offices, and they believe 
that one and the same department should advise, inspect, 
approve, and control. 
“May 23, 1871.” 
ON ATTRACTION CAUSED BY VIBRATIONS OE THE AIR. 
Professor Challis has communicated to the Philoso- 
phical Magazine a paper, in which he maintains that the 
condensation in waves propagated from a centre will vary 
inversely as the distance, and that the rate of diminution of 
the condensation or rarefaction with distance from the centre 
will be continually changed from the law’ of the inverse 
square of the distance to that of the simple inverse of the 
distance, provided there be alternate condensations and rare- 
factions, as seems to be inevitable ; for it is contrary to known 
hydrodynamical laws to suppose the possibility of a solitary 
wave of condensation. The above-mentioned velocity gives 
rise to a continual flow from the rarefied into the condensed 
parts, and just in the proportion required for altering the 
law of diminution with the distance from the inverse square 
to the simple inverse. Professor Challis believes that the 
attraction of magnetism is caused by vibration, to wffiich he 
might have added the attraction of gravity — a doctrine long 
since propounded by Robert Hooke, and of which an account 
is given in his posthumous works. In the revolving grate 
erected by Boulton and Watt beneath a steam-boiler at the 
Bank of England, the coal was fed by a scoop moved by a 
cam, which advanced the scoop gradually over an orifice, 
carrying coal wdth it, and then suddenly drew back the 
scoop, wffien the coal, by its inertia, remaining behind it, fell 
upon the fire. In this case we have a backward and for- 
ward motion causing bodies subjected to it to travel in a 
certain direction ; and if we suppose a similar motion to 
exist in the particles of bodies, an attraction like that of 
gravity will be the result . — Journal of the Society of Arts. 
