184 REPORTS ON INVESTIGATIONS AND PROJECTS. 



have been using, and upon which the value of our results very largely 

 depends, have therefore been made the subject of a searching examination. 

 The results of this purely physical investigation are not only of value to us, 

 but to all other investigators who have occasion to use high temperatures, to 

 technical laboratories, and to a considerable number of the important indus- 

 tries. They will therefore be embodied in a series of separate papers, of 

 which two are now ready for the press. These are concerned with the actual 

 tools of our daily measurements, and will be briefly reviewed under their 

 individual titles below. In addition to these, a fundamental investigation of 

 the gas scale, in terms of which all high temperatures are now expressed, is 

 well under way, and equipped with new and exceptionally perfect apparatus, 

 but no report upon it can be made during the present year. 



(11) Everyday problems of the moving coil galvanometer. Walter P. White. To 



appear in Phys. Rev. for November, 1906. 



A discussion of the conditions of construction and of adjustment of moving- 

 coil galvanometers in order to secure (i) high sensitiveness, (2) short 

 period, (3) suitable damping, (4) constancy of zero, and of the possibility 

 of obtaining some of these at the expense of others. The discussion has also 

 been extended to include ballistic systems. 



(12) The constancy of thermoelements. Walter P. White. To appear in Phys. Rev. 



for December, 1906. 



The main source of error in thermoelectric measurement is due to inhomo- 

 geneity in the wires of the thermoelement. This may be original, and due to 

 an imperfect distribution of the materials composing the wires, or may be 

 acquired by exposure to contamination in their daily use. In the two classes 

 of thermoelements in common use, platinum with platin-rhodium (Heraeus) 

 at high temperatures, and copper and constantan (an alloy of copper and 

 nickel) at low temperatures, we find no original impurity which need affect 

 temperature measurements by as much as o.oi per cent (equal to 0.01° at 

 100° or 0.1° at 1,000° C). The problem, therefore, resolves itself into an 

 effort to discover what are the agencies which cause deterioration of the ele- 

 ments, the character of the error produced by their presence, and whether or 

 not these substances can be excluded or rendered harmless. 



In copper-constantan elements, inhomogeneities appear from two sources : 

 (i) Variations in the hardness of the wire, due partly to unsatisfactory 

 initial annealing and partly to bending the wires when in use. The effects 

 of inadequate annealing are quite permanent at low temperatures, and are 

 best avoided by rejecting wires in which they are found. Drawing the 

 wire over the sharp corner of a board before using will usually produce uni- 

 form hardness, and no further trouble need then be feared from handling. 



