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IX. On Molecular Influences. —P art: I. Transmission of Heat through Organic 
Structures. By John Tyndall, F.R.S^ 
Received October 20, 1852, — Read January 6, 1853. 
The various solid substances which are met with in nature allow themselves to be 
classed under three general heads Amorphous, Crystalline and Organized. In 
amorphous bodies the component partieles are confusedly mingled, without any regard 
to symmetry of arrangement. In crystalline bodies, on the contrary, the particles 
are symmetrically arranged ; the mass appears as if built up according to certain 
architectural rules, and the result is an exterior form whose angular dimensions are 
perfectly constant for all crystals of the same class. Organized bodies, as the name 
implies, are bodies endowed with, or composed of, organs formed with reference to 
the special functions they are intended to discharge, and in the construction of which 
a molecular architecture of a very composite order comes into play. The granules, 
cells, glands, tubes, &c. of animal and vegetable tissues are all, of course, the 
visible products of this architecture. Crystalline bodies appear to bridge the chasm 
which separates the amorphous from the organized. Like the former, they are devoid 
of the powers of assimilation and reproduction — like the latter, their particles are 
arranged according to rule ; as if nature, in the case of crystals, had made her first 
structural effort. The student of nature has ever looked upon these molecular com- 
binations with an inquiring eye, and, perhaps, at no age of the world more than at 
present. The molecular peculiarities of any substance declare themselves by the 
manner in which a force is modified in its passage through the substance. The 
polarization and bifurcation of a luminous ray in doubly refracting media is an 
old example of molecular action ; and the rotation of the plane of polarization, 
observed by Professor Faraday, may be the result of a mechanical change of the 
medium, eflfeeted by the current or the magnet. Senarmont’s* and Knoblauch sj- 
experiments demonstrate the influence of crystalline structure upon the transmission 
of heat; and the rnagnecrystallic discoveries of Plucker and Faraday receive, I 
believe, their true explanation by reference, simply, to the modification of the mag- 
netic and diamagnetic forces which peculiarity of aggregation induces. Matter, in 
this aspect, may be regarded as a kind of organ through which force addresses our 
senses ; if the organ be changed, it is reasonable to infer that the utterance will be 
eorrespondingly modified, — an inference which is abundantly corroborated by ex- 
periment. Thus, mechanical pressure will polarize a ray, and the same may be 
* Annales de Chimie et de Physique, vols. xxi. xxii. xxiii. 
t Poggendorff’s Annalen, vol. Ixxxv. p. 169. 
