Dr. Wollaston on metallic titanium. 21 
gas are seen to rise from the surfaces of both the metals ; but, 
if a piece of paper be interposed between them, then no gas 
is given off by the copper. In a piece of paper, so placed 
between zinc and copper, I made a small hole, and after in- 
serting in it one of the cubes so as to be in contact with both 
the metals, I had the satisfaction to find an electric communi- 
cation completely established by this interposition, for gas 
was now given off from the surface of the copper. 
From the situation in which this metal is found, it evidently 
has no affinity for iron in the metallic state, and it seems 
equally indisposed to unite with every other metal that I have 
tried. Though it is evidently impossible to measure with 
precision the specific gravity of such specimens as I first re- 
ceived for analysis, I was in hopes of trying whether one of 
the largest of the cubes would sink or swim in melted tin, 
and for that purpose endeavoured to tin its surface, but I 
could not succeed in uniting it with either tin or lead, with 
silver or copper, and had no encouragement to prosecute 
farther a series of negative results, in search of metals for 
which it may have an affinity. 
From the extreme infusibility of these cubes, it seems pro- 
bable that they have not been formed by crystallization in 
cooling from a state of fusion, but have received their suc- 
cessive increments by reduction of the oxide dissolved in the 
slag around them : a mode of formation to which we must 
have recourse for conceiving rightly the formation in nature 
of many other metallic crystals. 
Since the date of this communication, the liberality of Mr. 
Anthony Hill, of Merthyr Tydvil, has supplied me with a 
