112 



Mr. F. C. Penrose. Some Additional 



group as they are seen when a 1 per cent, solution and graphite 

 electrodes are used, and of two isolated lines which are less refrangible ; 

 with them are compared the lines photographed from other more 

 dilute solutions. The sodium line X 3301 appears as a long line in 

 the 1 per cent, solution and becomes shorter as the quantity of sub- 

 stance is reduced. 



Observations were carried as far as a solution containing -000001 

 per cent, of silicon, the two strongest lines being still visible, but as 

 the photographs of these more dilute solutions have been damaged by 

 being kept so long a time in the atmosphere of the chemical laboratory, 

 they are not now available for similar measurements. 



As the sodium lines are suppressed when the silicon lines are strong, 

 the two carbon lines are also reduced very much in length and strength. 

 This is very easily observed on account of the close proximity of the 

 silicon lines, the wave-lengths of the two carbon lines being 2508*7 

 and 2511-6 (Hartley and Adeney). In the more dilute solution, these 

 lines are observed to be lengthened until they become of the normal 

 dimensions of 20/100ths of an inch. It thus appears more than probable 

 that the suppression of the sodium does not result from any chemical 

 action within the spark discharge, such as might be supposed to occur 

 if the sodium were dissociated from the compound, and being in 

 contact with a silicate were to liberate silicon, or to combine with silicon 

 directly, and in presence of water give rise to the formation of silicon 

 hydride. 



The suppression of much of the sodium spectrum, and the shorten- 

 ing and weakening of the carbon lines, is more likely to be a purely 

 physical phenomenon than the result of any chemical reaction in 

 the spark. 



" Some Additional Notes on the Orientation of Greek Temples, 

 being the Result of a Journey to Greece and Sicily in April 

 and May, 1900." By F. C. Penrose, M.A., F.R.S. Eeceived 

 January 17, — Read February 14, 1901. 



(Abstract.) 



The paper contains notes on two examples from Greece and four 

 from Sicily — of these, three are of the nature of amplification and 

 correction, and three are fresh cases. 



(1.) To the second head belongs a rude and archaic shrine in the 

 Isle of Delos ; not improbably the most ancient existing example of a 

 religious structure on Greek soil. It exhibits the usual stellar con- 

 nection with its orientation and an approximate date conformable with 

 its remote antiquity (1530 B.C.). 



