

BAIRD &TATLOCK (LONDON) LTD. 



Indicators. Two types of indicating instruments are made, the Wall Type (see Fig. i), for fixed use, 

 in a metal case with nickel-finished front ; and the Portable (see Fig. 2), in a polished hardwood case with a 

 leather carrying handle. In both indicators the moving coil which carries the pointer over the scale is mounted 

 on PATENT SPRING-MOUNTED JEWELS, thus providing a frictionless movement guarded against damage 

 by rough usage. The Wall Type Indicator has an adjustable red index which can be set to any desired tempera- 

 ture, and the user can then see from a distance when the black moving pointer departs from the desired 

 temperature (see Fig. i). 



Recorder. Where a permanent record of the temperature is to be kept, an automatic recorder is used. 

 This instrument draws an ink line on a paper chart, thus showing what the temperature has been at all times. 

 A chart of this kind is essential where regularity of work is required. The temperature may be read from the 

 recorder at any instant without disturbing its record, and after the heating is over the record chart, showing 

 the whole temperature history of the work, can be filed for reference with other particulars of the job in hand. 



Absence of Pen Friction. In order to avoid errors due to friction of the pen upon the chart, a special 

 design is employed (see Fig. 4). The marking pen swings freely in front of, Jsut not touching the chart. Periodi- 

 cally the pen is pressed upon the chart by a clock-driven presser bar, thus leaving a dot which records the tempera- 

 ture. The successive dots join into a continuous line showing the rise and fall of the temperature. The pen has 



Fig. 4. Automatic Recorder. 



About one-seventh full size. 



an inking device which takes up ink from a pad on the presser bar and transmits it to the paper, the particular 

 construction preventing excess of ink, which would make a blot, and at the same time one charge of ink on the 

 presser bar lasts for several days. The moving coil which controls the pen is carried by PATENT SPRING- 

 MOUNTED JEWELS, similar to those in the Indicators, and it is not liable to damage due to vibration. There 

 is no delicate suspension to break. 



Charts. The recorder charts are circular, ten inches in diameter, thus allowing the whole of a record to 

 be seen without disturbing the recorder. They are printed for one revolution in twenty-four hours, but it is 

 possible to allow the same chart to run two or three days, as, for instance, over Sunday, or to cover the whole 

 firing of a pottery kiln, the line for each day being readily distinguished. The temperature scale is open, thus 



ICHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



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