430 J. N. Lockyer— Existence of Hlements in the Sun. 
battery power or metallic electrodes, the small ones those of 
observers using small battery power, or the chlorides. If the 
lists of the latter class of observers be taken, we shall have only 
the longest lines, while those omitted by them and given by the 
former class will be the shortest lines. 
In cases therefore in which I had not mapped the spectrum 
by the new method of observation referred to in my paper, I 
have taken the longest lines as thus approximately determined ; 
for it seemed desirable, in view of the very large number of 
unnamed lines, to search at once for the longest elemental lines in 
the solar spectrum without waiting for a complete set of maps. 
A preliminary search having been determined on, I endeav- 
oured to get some guidance by seeing if there was any quality 
which differentiated the elements already traced in the sun from 
those not traced; and to this end I requested my assistant, Mr. 
R. J. Friswell, to prepare two lists showing broadly the chief 
chemical characteristics of the elements traced and not traced. 
This was done by taking a number of the best known com- 
pounds of each element (such, for instance, as those formed 
with oxygen, sulphur, chlorine, bromine, or hydrogen), stating 
after each whether the compounds in question were unstable or 
stable. ere any compound was known not to exist, that 
fact was indicated. 
Two tables were thus prepared, one containing the solar, the 
other the more important non-solar elements (according to our 
knowledge at the time). 
These tables gave me, as the differentiation sought, the fact 
that in the main the known solar elements formed stable oxygen- 
probability to exist in the solar reversing layer. Should the 
presence of ceriwm and uranium be subsequently confirmed, 
most of the iron group of metals will thus have been found in 
the sun. 
As another test, certain of those elements which form un- 
stable compounds with oxygen were also sought for, gold, silver, 
mercury being examples. ene of these were found. — 
he same result occurred when the lines due to the jar-spark 
taken in chlorine, bromine, iodine, and those of some 0 the 
other non-metals were sought, these being distinguishable as a 
group by formation of compounds with hydrogen. 
* Potassium has since been added. 
