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1879 *] Proceedings of Societies . 
carried successively to lower levels, leaving here and there banks 
of sand and gravel at various heights on the hill sides. These 
destructive floods, combined with the incessant river inundations 
due to the same general thaw of the great ice-sheet, carried 
down and spread out in the valleys and plains the great beds of 
gravel and sand which — with the modifications since brought 
about by long-continued fluviatile action — have given rise to 
various forms of escars, terraces, and other less-defined accumu- 
lations of these detrital materials. 
May 15. — “ Some Researches with Professor Hughes’s new 
Instrument for the Measurement of Hearing — the Audiometer,” 
by Benjamin Ward Richardson, M.D., LL.D., F.R.S.* The 
Audiometer consists of two Leclanche cells for the battery, a 
new and simple microphonic key connected with the cells and 
with two fixed primary coils, and a secondary or induCtion-coil 
the terminals of which are attached to a telephone. The induc- 
tion-coil moves on a bar between the two fixed coils, and the bar 
is graduated into 200 parts, by which the readings of sound are 
taken. The graduated scale is divided into 20 centims., and 
each of these parts is subdivided into 10, so that the hearing 
may be tested from the maximum of 200 units to o° — zero. 
The fixed coil on the right hand contains 6 metres of wire ; the 
fixed coil on the left hand contains 100 metres. By this means 
a long scale from the left-hand coil is produced. The secondary 
coil contains 100 metres of wire. In using the instrument, one 
Leclanche cell has been found sufficient, as a general rule ; but 
two have been used in instances where the hearing of the person 
under test has been very defective. The person whose hearing 
is being tested should sit in an easy position, and should not see 
the act of the observer in moving the microphone key. For 
good observation the room in which the experiment is made 
should be large, and all external causes of sound — such as the 
ticking' of clocks, the vibrations of windows and doors, the 
moving of feet, and the singing from gas jets — should be silenced. 
The sitter should close the ear that is not applied to the tele- 
phone while he is listening for minute sounds, and should give 
his full and calm attention to the proceeding. The instrument 
may be considered to afford the most satisfactory means for 
testing the hearing power of all persons who can define a sound. 
The range of sound is sufficient at the maximum, 200% for every- 
one who is not absolutely deaf o°, or zero, is a point of positive 
silence from the instrument, or rather from the sound which it 
produces through the telephone. One of the first facts learned 
with the audiometer is the suddenness with which the sound is 
lost to those who are listening. The sound is abruptly lost 
within a range of 2° ; that is, within one-hundredth part of the 
* For a description of Prof. Hughes’s indu&ion-currents balance see p. 508. 
