SCIENTIFIC SUMMARY. 
331 
light ; for the two microphones being held to the lips of the communicating 
parties, and the telephones to their respective ears, each observer hears a 
note sung by the other, but not that which he is himself simultaneously 
emitting. The explanation of this undoubted phenomenon is somewhat 
obscure. 
Dr. C. William Siemens, at a discussion before the Society of Telegraph 
Engineers, referred to the intimate connection between the microphone and 
its two elder sisters, the telephone and phonograph, in conjunction with 
which it formed a discovery which would probably be hereafter regarded as 
one of the greatest achievements in natural science of the present century. 
He further compared the phonograph with the action of the brain in the 
exercise of memory, the external impressions being communicated to 
corpuscular bodies imbedded in grey substance, and connected with the 
nervous system of volition. Fresh impressions may be understood to give 
rise then and there to acts of will, but how stands the case with impressions 
communicated years before, and, as we term it, “ Committed to Memory” P 
In order to this, the mind must have some power of reproducing a material 
record by which the impression has been rendered permanent. Such a 
hypothesis might also explain the confused images of dreaming, and the 
more vivid recollection of what occurred in early life, when the mechanical 
record may be supposed to have been distinct and indelible. It was also 
possible, by studying the action of selenium substituted for carbon in the 
microphone, that the impressions received by the retina would be equally 
susceptible of storage. The record itself might be supposed to be mechanical,, 
more probably, molecular, at any rate, material. 
Mr. Seabrooke points out that the microphone does not, strictly speaking, 
magnify the original sound, but substitutes for it a varying electric current 
of extreme rapidity. “In gently brushing the stand of the instrument, 
sound is heard in the telephone, but it does not at all follow that what we 
hear is a magnified reproduction of the brushing sound, for if the rapidity of 
the vibrations is insufficient to produce a sound, still they may move the 
carbon sufficiently to produce alternations of current, each of which may be 
able to set up vibrations of the telephone plate in its own period, or a modi- 
fication of it.” 
Mr. E. J. M. Page introduces a Du Bois Reymond’s induction coil by 
its primary into the microphonic circuit, the secondary coil being con- 
nected with a Lippmann’s capillary electrometer, which immediately gives 
large and definite movements of its column. 
Sir Henry Thompson demonstrated the surgical value of the microphone 
on June 4, in the Anatomical Theatre of University College. The soimd 
used for detecting stone in the bladder was connected with the circuit, and 
whenever it struck the smallest fragment of calculus, the result was clear 
and unmistakable. Bullets and fragments of bone, he stated, might, by a 
similar process, be discovered. 
On the day previous to Sir H. Thompson’s demonstration, Mr. James 
Blyth brought before the Royal Society of Edinburgh a still simpler form of' 
the microphone. He includes in the circuit “ a small jelly can,” half filled 
with cinders broken into coarse fragments, the connection being made by 
slipping down at opposite sides, between cinders and jar, two slips of tin 
