7 2 Proceedings of the Royal Society 
6. In cold dilute sulphuric acid (1 to 4), the nickel lost 0*14 per 
cent., and behaved on heating as with the last acid. 
When nickel articles, such as those before you, are heated over 
an Argand or Bunsen burner, a thin unweighable coating of oxide is 
formed (which can be removed by sand-paper), the nickel vessel 
becoming very dark in colour. 
Caustic soda can be fused in a nickel basin with scarcely any 
change in weight. In one experiment, where the caustic soda was 
fused for one hour in a small nickel basin, the gain in weight 
amounted to OBIS per cent, 
These, then, are a few of the experiments that I have been able to 
make with this metal ; some of them proving the value of nickel for 
many purposes to which it has hitherto not been applied. 
2. Note on a Singular Passage in the Principia , 
By Professor Tait. 
In the remarkable Scholium , appended to his chapter on the 
Laws of Motion, where Newton is showing what Wren, Wallis, and 
Huygens had done in connection with the impact of bodies, he uses 
the following very peculiar language : — 
“Sed et veritas comprobata est a D. Wrenno coram Regid 
Societate per experimentum Pendulorum, quod etiam Clarissimus 
Mariottus Libro integro exponere mox dignatus est.” 
The last clause of this sentence, which I had occasion to consult 
a few days ago, appeared to me to be so sarcastic, and so unlike 
in tone to all the context, that I was anxious to discover its full 
intention. 
Not one of the Commentators, to whose works I had access, 
makes any remark on the passage. The Translators differ widely. 
Thus Motte softens the clause down into the trivial remark 
“ which Mr Mariotte soon after thought fit to explain in a treatise 
entirely on that subject.” 
The Marquise du Chastellet (1756) renders it thus : — 
“ mais ce fait Wrenn qui les confirma par des Experiences 
faites avec des Pendules devant la Societe Boyale : lesqelles le 
celebre Mariotte a rapportees depuis dans un Trait4 qu’il a compost 
exprks sur cette matiere.” 
