EEPOETS 



ON THE 



STATE OF SCIENCE. 



Second Report of the Committee, consisting of Professor G. Forbes 

 (Secretary), Captain Abnet, Dr. J. Hopkinson, Professor W. G. 

 Adams, Professor Gr. C. Foster, Lord Katleigh, Mr. Preece, Pro- 

 fessor Schuster, Professor Dewar, Mr. A. Vernon .Harcourt, 

 Professor Atrton, and Sir James Douglass, appointed for the 

 pui^ose of reporting on Standards of Light. Drawn up hy 

 Professor Gr. Forbes. 



The Committee on Standards of Light met repeatedly during last 

 winter. It had been proposed in last year's report to carry on experi- 

 ments on electrical standards in the hope of arriving at an absolute 

 standard of light. One of the first steps was to discover a means of re- 

 pK)ducing a definite temperature, and certain experiments were proposed 

 for this purpose. At one of the first meetings of the Committee Captain 

 Abney announced that he had already found a means of doing this in a 

 different manner from that proposed in the Committee's report and de- 

 pending only upon the change of resistance of the carbon filament. Under 

 these circumstances the Committee left this part of the experimental in- 

 vestigation to be reported upon by Captain Abney. His further researches 

 have, however, led him to believe that the law which he had announced 

 to the Committee does not hold with all qualities of carbon filament. He 

 has, however, been engaged upon further experimental researches, which 

 are almost ready for publication, and which have an important bearing 

 upon the labours of the Committee. 



In last year's report attention was drawn to the value of the Pentane 

 standard of Mr. Vernon Harcourt as a practical reproducible standard, 

 and Mr. Rawson has been since then engaged in a further examination of 

 this standard. Sir James Douglass has also made some experiments 

 which are not quite completed, but have gone so far as to give great pro- 

 mise. Some account of these experiments in this report had been ex- 

 pected by the Committee, but the absence of Sir James Douglass on 

 official business has interfered with this. 



At one of the first meetings of the Committee the Secretary showed 

 what he had done in the way of improving thermopiles such as it was 

 hoped would be of use in the investigations recommended in last year's 



