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The author gave several extracts from the able address of the 
President (Sir W. Armstrong) delivered at the last meeting 
of the British Association — Newcastle, August, I860 — 
wherein Sir William, in support of the mechanical theory of 
heat, adduced several facts and considerations which appear 
inconsistent with that doctrine, or the non-materiality of 
heat ; and as he assumed the dynamical theory of heat to be 
probably the most important discovery of the present century, 
Mr. Dyer was led by the same facts and considerations, as 
well as by many others which be has himself adduced, to 
conclude that no such definitive discovery has been made in 
our times, and that the question as to the entity or nonentity 
of heat remains in the like obscurity in the present as it was 
in the beginning of the last century. 
The author then quoted some passages from the lectures of 
Professor Tyndall, “on the forms and action of water,” and 
on radiation through the atmosphere, wherein the Professor 
had assumed that great mechanical forces were exerted in 
the combination of the gases to form water, as also in the 
changes of water from its several conditions of solid, liquid, 
and vapour, and vice versa , giving the sum of such forces in 
equivalents of a ton weight falling from different heights ; 
which phenomena Mr. Dyer considers as solely due to the 
chemical forces called into action by those changes in the 
forms and action of water ; and as the latter class of forces 
consists of the affinities and repulsions of the particles of the 
water excited by the different degrees of heat combined there-* 
with, the assumption of such mechanical forces being exerted 
in those mutations is untenable. 
In giving the results of his interesting experiments of 
the absorption of heat by aqueous vapour in the air, and 
of its free radiation through dry air, the Professor says 
that “ this newly discovered property of transparent aqueous 
vapour must exercise immense influence on the pheno- 
mena of meteorology but Mr. Dyer gave quotations 
