470 



Sir W. Ranisay and Prof. J. N. Collie. [May 18, 



meteorologists to form a more definite idea of the prospects of 

 approaching seasons. 



We wish to express our thanks to Dr. W. N. Shaw, F.R.S., who 

 has kindly assisted the work by permitting us to utilise the valuable 

 collection of pressure data deposited in the archives of the Meteoro- 

 logical Office. 



We also owe a debt of gratitude to Messrs. W. Moss and 

 T. F, Connolly, who have shown great zeal in completing the 

 necessary computations and drawing the numerous curves which were 

 required for the different stations that have been investigated. 



" The Spectrum of the Radium Emanation." By Sir William 

 Ramsay, K.C.B., F.R.S., and Professor J. Norman Collie, 

 F.R.S. Received May 18 —Read May 19, 1904. 



Attempts have been made since July, 1903, to see and map the 

 spectrum of the emanation from radium, for at that date the con- 

 version of the emanation into helium was observed by Ramsay and 

 Soddy, and during the first discharge of the induction current through 

 the emanation, it was believed that a peculiar spectrum was noticed ; 

 indeed, three lines were persistent, and were mentioned in the 

 communication on the subject in these 'Proceedings.' 



But such attempts have uniformly failed ; at the first moment of the 

 discharge, indeed, a brilliant spectrum has twice been observed, which 

 soon became confused and indistinct. It faded before it was possible 

 to map it, and owing to the presence of impurities, generally carbon 

 monoxide, nitrogen, or hydrogen, the special spectrum was obscured. 

 All that could be said was that it appeared to present some brilliantly 

 green lines. 



These experiments, however, have not been fruitless ; they have led 

 to better knowledge of the precautions which it is necessary to take 

 to eliminate impurities. The arrangement of the apparatus, too, has 

 been simplified, and the manipulation made easier. As it is possible 

 that others may wish to repeat the experiments, and may perhaps 

 have even better success in mapping the spectrum, we think it well to 

 enter into the details of the manipulation somewhat minutely, and 

 to give a woodcut of the apparatus employed. 



The stock of radium bromide (about 109 milligrammes) dissolved in 

 about 10 c.c. of water in two small bulbs was attached by sealing to a 

 small Topler's pump. Between the pump and the bulb there was 

 a stop-cock, greased, of course, to insure freedom from leakage ; but in 

 order to prevent the long contact of the emanation with the stop-cock, 

 and its possible contamination with carbon dioxide, the mercury from 



