8 



SUPPLEMENT. 



but, in the absence of such force it is held out of action by a spring. The 

 auxiliary brake serves for immediate and temporary use in the event of 

 the friction-line or the connecting-belt parting, and in unusually heavy 

 seas and under adverse circumstances it may be used in lieu of the toggle 

 tucked into the friction-line — described in the original volume. The office 

 of the toggle — although it is rarely used — is to impose upon the reel a 

 small amount of friction which will not be lessened by the action of the 

 governor, 1 the object being to permit in heavy seas a rapid rate of paying 

 out. 2 The occasional advantage which may be derived from this acces- 

 sory is well illustrated by such an extreme case as would make the use of 

 the auxiliary brake desirable, thus: sounding'from the bow; sea heavy; 

 ship pitching violently; a heavy reel in use. and containing a large coil 

 of wire which adds much to its weight at the periphery. 3 Under these 

 conditions, and when the reel is revolving with considerable speed, the 

 vessel rises suddenly, increasing the tension upon the wire which is 

 being payed out; the cross-head is borne down, easing the friction-line, 

 we will assume, more than is desirable, and the heavy reel, thus deprived 

 for a second of nearly all frictional control, is set revolving with great 

 rapidity. At this instant the vessel gives a quick, deep plunge. The 

 reaction of the accumulator acting as a governor is almost instantaneous, 

 and the friction-line is set hard taut ; but before the momentum of the 

 heavy reel can be overcome the wire slacks and perhaps flies from the 

 reel. If, in the case stated, the auxiliary brake, which is independent of 

 the governor, had been bearing upon the reel with a constant pressure, 

 maintaining a slight resistance, the undue slacking of the friction-line 

 would not have been followed by such excessive revolution of the reel. 

 To insure an even pressure of the auxiliary brake, the inboard end of the 

 brake-lever — the long-arm — might be connected with the bed of the sound- 

 ing-machine by a spring of rubber or metal which could be set to any 

 desired tension. It must not be inferred that the auxiliary brake is a 

 necessity; it is intended as a convenience on extraordinary occasions, to 

 obviate the necessity for unusual skill or judgment on the part of those 



1 Page 6.8, H 6. 



2 Page 70, H 2. 



3 Page 56, If I. 



