JULY 22, 1915] 
NATURE 
579 


meters have given special attention to recorders, 
have devised arrangements for registering the re 
ings of several pyrometers simultaneously. For resist- 
ance pyrometers the well-known recorder of Callendar 
is much used, and the modern form of Roberts-Austen 
photographic recorder, made by the White Instrument 
Company, is of great service in accurate work with 
thermo-electric instruments. Of the more recent types 
Foster’s recorder (Fig. 7) possesses an indicator 
pivoted horizontally, the pointer being vertical and 


Instrument Company has been improved in many 
details. One of the latest forms is shown in Fig. 8, 
in which two indicators are made to record on a 
single chart wound on a long drum rotated by clock- 
work. The presser-bar in this case pushes the pointer 
on to an inked thread, which touches and leaves an 
ink-dot on the graduated chart. By having two 
threads, coloured with different inks, and a 
mechanism which brings each thread in turn beneath 
the pointer, four simultaneous records may be taken, 
the pyrometers concerned 
being automatically switched 
on to the indicators in correct 

















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sequence. 
A recorder in which the 
mechanism is driven by a 
motor has been introduced 
by the Leeds and Northrup 
Company, and is much used 
in the United States. R. W. 
Paul has also adopted the 
motor-drive in his new 
recorder (Fig. 9), which 
also embodies other novel 
features. The chart is made 
in the form of a continuous 
roll, lasting for tooo hours, 





























Fic. 9.—Paul's recorder. 
moving across a circular chart rotating about its centre 
once in twenty-four hours, At short intervals a 
presser-bar is urged against the pointer, at the end 
of which is placed a capillary tube containing an inked 
wick. A mark is thus made on the chart correspond- 
ing to the position of the pointer; and as the lines 
radiating from the centre are divided into tem- 
peratures, a complete record, visible in its entirety, 
is made. 
The thread recorder of the Cambridge Scientific 
NO. 2386, VOL. 95] 
a large part of which is open 
to inspection through a win- 
dow extension. The pointer 
is pressed periodically on to 
an inked ribbon, which 
Fic. 8.—Double thread recorder. 
touches the chart at a place where the latter 
is passing over a_ knife-edge, and hence a dot 
is produced. Change-gear for altering the speed 
may be inserted when desired, and duplicate 
records are secured by means of a second ribbon, of 
different colour, which may be made to alternate in 
position with the first ribbon beneath the pointer. 
When a resistance pyrometer is in use, a Harris 
indicator replaces the galvanometer, a new chart, 
divided to suit this indicator, being inserted. 
