448 A. G. Compton—Method of obtaining Autographie 
been broken several times, not merely by the maximum In- 
ward vibration of the membrane, but by several preceding and 
following it. But generally, these dots flow together, and 
only appearas a dash. In the accompanying specimen records, 
the dashes have a length equal to that of about three siren-rev- 
olutions or thirty vibrations. 
or membranes, I have used thin sheet rubber, paper, gold- 
beater’s skin, thick vuleanized rubber (about 2™™), and leather. 
The best results have been obtained with white kid such as 
is used in the making of organ bellows. The membrane 
by means of a thread wound round asmall wrest-pin.. 
The exactness of the coincidence between seconds and siren 
tion of the break in the siren-circuit at A over the duration 
of the siren contact at S. If the whole siren contact 1s comncl 
dent with any portion of the break a, the siren-record will be 
