148 Intelligence and Miscellaneous Articles. 



partially closed, so as to induce a commencement of solidification ; 

 the cock was again touched ; and by thus modifying the arrival of 

 the gas, it was kept, without too much difficulty, just at the point 

 of fusion. The great mass of the furnace secures a sufficiently 

 extensive constant thermal field, and permits its constancy to be 

 easily maintained. 



The operation was precisely the same for bringing the platinum 

 to and keeping it at 954°, the outer crucible containing silver 

 instead of gold. 



It is rather more difficult to accomplish the operation in the pal- 

 ladium bath ; it can, however, be done by feeding the furnace with 

 a Schloesing blowpipe and protecting the crucibles by graphite 

 casings. Palladium can also be made use of more simply, even at 

 its melting-point, by employing Deville and Debray's furnace and 

 blowpipe. 



For the photometric measurements I employed successively the 

 two methods by which luminous intensities are usually measured — 

 the comparison of two contiguous luminous fields, and the extinc- 

 tion of the isochromatic lines called forth by a sensitive polariscope. 

 I used for this purpose the Grouy spectrophotometer and a Trannin 

 spectrophotometer, suitably modified for the present use ; and 

 although each of these apparatus suits better than the other in cer- 

 tain cases, I thus obtained a valuable control of the results. The 

 source taken as the term of comparison, in all the experiments, was 

 the Carcel standard lamp burning 42 grams of oil per hour. 



The following Table contains the results thus obtained, plus 

 those of a series made at 775° (temperature measured by the calo- 

 rimetric method). 



Temperatures. X=656. 

 C. 



775 0-00300 



954 0-01544 



1045 0-0505 



1500 2-371 



1775 7-829 



Intensities. 



X = 5892. 



A =535. X=482. 



D. 



(E=527) (F=486) 



0-00060 



0-00030 



2-01105 



0-00715 (?) 



0-0402 



0-0265 0-0162 



2-417 



2-198 1-894 



8-932 



9-759 12-16 



If, then, the luminous intensity of incandescent platinum at 

 954°, 1045°, and 1500°, in the various simple radiations, be suc- 

 cessively taken for the unit, we get for the relative intensities : — 



775 . 



. 019 



0-05 004 





954 . 



. 1 



1 1 





1045 . 



3-27 1 ... 



364 1 ... 371 1 ... 



1 



1500 . 



.154 47 1 



219 60 1 307 83 1 



117 1 



1775 . 



. 507 155 3-30 



809 222 370 1365 368 444 



752 64. 



Various consequences follow from these numbers, both for the 



