4 PLEASANT WA YS IN SCIENCE. 



reasons for regarding hydrogen as a metallic element, strange 

 though the idea may seem to those who regard hardness, 

 brightness, malleability, ductility, plasticity, and the like, 

 as the characteristic properties of metals, and necessarily 

 fail to comprehend how a gas far rarer, under the same 

 conditions, than the air we breathe, and which cannot 

 possibly be malleable, ductile, or the like, can conceivably 

 be regarded as a metal But there is in reality no necessary 

 connection between any one of the above properties and 

 the metallic nature ; many of the fifty-five metals are wanting 

 in all of these properties ; nor is there any reason why, as 

 we have in mercury a metal which at ordinary tempera- 

 tures is a liquid, so we might have in hydrogen a metal 

 which, at all obtainable temperatures, and under all obtain- 

 able conditions of pressure, is gaseous. It was shown by 

 the late Professor Graham (aided in his researches most 

 effectively by Dr. Chandler Roberts) that hydrogen will 

 enter into such combination with the metal palladium that 

 it may be regarded as forming, for the time, with the palla- 

 dium, an alloy; and as alloys can only be regarded as 

 compounds of two or more metals, the inference is that 

 hydrogen is in reality a metallic element 



Fourteen only of the elements known to us, or less than 

 a quarter of the total number, were thus found to be present 

 in the sun's constitution; and of these all were metals, if 

 we regard hydrogen as metallic. Neither gold nor silver 

 shows any trace of its presence, nor can any sign be seen 

 of platinum, lead, and mercury. But, most remarkable of 

 all, and most perplexing, was the absence of all trace of 

 oxygen and nitrogen, two gases which could not be supposed 

 wanting in the substance of the great ruling centre of the 

 planetary system. It might well be believed, indeed, that 

 none of the five metals just named are absent from the sun, 

 and indeed that every one of the forty metals not recognized 

 by the spectroscopic method nevertheless exists in the sun. 

 For according to the nebular hypothesis of the origin of our 

 solar system, the sun might be expected to contain all the 



