of Edinburgh, Session 1885-86. 625 
by the hypothesis that the heads were held over heated stones after 
being taken from the infusion of herbs. There is room enough to 
speculate. I think, however, the speculation is warranted by (may 
it not be said) the attainments of some of the Upper Amazon tribes 
in organic chemistry ! How otherwise can we account for their 
skill to separate, by a complex process, the starch in the tubers of 
the manioc plant ( Janipha manihet) from the strong narcotic poison 
they contain, and to give to the people the former as a nutritious 
bread — farinha or cassava — the “ Bread of Brazil 1 ” Or, even, 
how otherwise could they prepare from other plants the arrow 
poison, or woorare ? It would not be a great surprise to learn 
that, having gouged the bones from scalp and face-skin, their skill 
as herbalists, aided by a little careful manipulation, enabled them to 
realise these shrunk heads. As regards their meaning, it seems to 
me we have information enough on this point to warrant the in- 
ference that they were used by the native priests as oracles, and 
that the strings, with their blood-red marks, were connected with 
this use. 
Monday, 1st March 1886. 
Professor DOUGLAS MACLAGA1ST, Vice-President, 
in the Chair. 
The following Communications were read: — 
1. On the Magnitude of the Mutual Attraction between two 
pieces of matter at distances of less than ten micro- 
millimetres. By Sir William Thomson, Hon. V.P. 
2. On a Theorem in the Science of Situation. By 
Professor Tait. 
3. On Radiation from Snow. By John Aitken, Esq. 
2 T 
VOL. XIII. 
