HOLMAN. — PYROMETRY. 243 



wires. By watching ttie surface appearance of tlie globule closely, it 

 is easily possible to control the position and effect of the flame so as 

 to maintain the mass just on the point of fusion and get a fairly con- 

 stant reading. Heavily clouded dark glasses must be used in watch- 

 ing the platinum. Neglect of this involves risk of serious permanent 

 injury to the sight, and, if persisted in, of even greater danger. 



3Iodijications of the Le Chatelier Thermo-electric Pyrometer. — By 

 an experience extending over four years in the use of this instrument 

 in its original form, and after tests and study of many other forms 

 of pyrometer, the writer is convinced both that the thermo-electric 

 method is by far the most promising one as the basis for industrial 

 pyrometer, as well as for much measurement in scientific research, 

 and that the Le Chatelier form of the instrument is the most generally 

 satisfactory one now obtainable on the market. Yet for general in- 

 dustrial services the Le Chatelier instrument falls short of the require- 

 ments in two ways. First, it is not sufficiently simple of manipulation 

 in the setting up, and in the calibration, to be put into the hands of 

 any but a fairly well trained observer. A trained chemist of works, 

 an educated superintendent, or any man of such caliber may be ex- 

 pected to take the instrument as sent by the makers, mount it, and 

 operate it successfully ; and under such observers it is doing important 

 service in many places. The mere reading can be done by any fore- 

 man after a few words of explanation. Secondly, the conditions of 

 support requisite for the galvanometer, although often obtainable, are 

 by no means commonly to be found in those portions of industrial 

 works where it would be otherwise advantageous to locate the instru- 

 ment. These facts are restricting the introduction of an instrument 

 otherwise excellent in its performance and marking a distinct onward 

 step in the art of practical pyrometry. 



The urgent need of a still more universally practicable pyrometer 

 cannot be too strongly nor too often emphasized. In a large number 

 of industrial processes of great magnitude the employment of a reli- 

 able pyrometer would certainly result in a notable advance in quality 

 of product, in prevention of waste, in improvement or perfection of 

 the process itself, and in the discovery of new methods and new 

 products. If a galvanometer as reliable, as simple, and as portable 

 as the Weston magnetic voltmeter could be directly connected to a 

 rhodo-platinum thermal couple, there would result, as I have for some 

 years urged, an almost ideal pyrometer for technical work. Thus far, 

 unfortunately, the Weston instruments do not yield in this combination 

 sufficient sensitiveness to admit of their being put forward as meeting 



