TRANSACTIONS OF SECTION A. 



561 



Lamp No. II. 



No. of Ex- 

 periment 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



CeUs 



40 

 42 

 43 

 44 

 46 

 50 

 52 

 54 

 56 

 58 

 40 

 42 

 60 

 62 

 66 

 70 



Volts 



Webers 



89-7 



93-3 



95-4 



98-8 

 103-0 

 106-9 

 110-8 

 1170 

 119-8 

 121-8 



87-0 



89-7 

 122-8 

 126-0 

 132-4 



Carbon 



2-207 



2-296 



2-38 



2-49 



2-63 



2-74 



2-85 



2-95 



2-95 

 •2-98 



2-14 



2-24 



3-06 



3-13 



3-24 

 of lamp 



Volts X 

 webers -^10= 

 kilogram- 

 metres 



19-8 

 22-42 

 22-71 

 24-60 

 27 09 

 29-29 

 31-56 

 34-53 

 35-34 

 36-29 

 18-62 

 2009 

 37-58 

 39-44 

 42-89 

 broke. 



Caudles per 

 borse-power 



181 

 234 

 245 

 306 

 316 

 367 

 440 

 417 

 388 

 361 

 140 

 156 

 365 

 340 

 383 



Lamp No. III. 



Some of the irregularities of the results in the preceding tables are very inter- 

 esting and important, as showing the effect of the blackening of the glass by 

 volatilization of the carbon when too high electric power came to be applied. 



The durability of the lamp at any particular power must be tested by months' 

 experience before the proper intensity for economy can be determined. 



6. On Photometry, with Experiments. Bi/ Professor Sir William 

 Thomson, M.A., F.B.8. 



7. On the Dynamical Theory of Badiation} 5z/ Professor Aethpe 

 Schuster, Fh.B., F.B.S. 

 All theoretical investigations on radiation and absorption are confined to 

 the consideration of an enclosm-e of uniform temperature. As no observation can 

 be carried on in such an enclosure the theoretical results can only be adapted to 

 the actual phenomena by making an assumption contained in Prevost's law that 

 the radiation of the body is a function of the temperature only. It is the object 

 of this paper to give some considerations which tend to show that this assump- 

 tion is not justified. Imagine a Bunsen burner witli a soda bead in it. The 

 spectroscope wLU show the well-known yellow .sodium lines; but we know that 

 the sodium molecide is also capable of sending out certain rays in the green part of 

 the spectrimi. These rays are so weak, in tlie case under consideration, that they 

 escape observation. We conclude from the appearances that the internal radiation 



1881, 



Printed in full, P/iil. Jfat/., October 1881. 

 



