Chemistry and Physics. 125 
Tyndall then proceeded to show that a bar of magnetic or of diamagnetic 
matier might be caused to set axal or equatorial, by simply varying its 
point of suspension. The experiments were closely watched by Prof. 
Thomson, who certified the success of every one of them.  ‘ Now,” 
proceeded Dr. Tyndall “ we have here two substances, exactly alike in 
exterior shape,—one a crystal built by nature, the other a model con- 
structed by myself; you have seen that the actions of both are iden- 
tical—the one is not to be distinguished from the other. Whatever 
explains the deportment of the model must explain that of the crys- 
This piece of wax is composed of material particles; now I 
ask; what must the effect be if I squeeze this wax between two plates ? 
will it not be to bring the particles more closely together along the line 
on which the pressure is exerted? This is simply what has been done 
in the case of the model, and this peculiar arrangement of its particles 
(without reference to their shape) produces. the effecis which you have 
Witnessed. Now, the action of the model comes under the head of 
totally inadequate to its explanation. Magno-crystallic action is thus 
Proved to be due, not to the shape of the ultimate molecules, but to 
their manner of arran ement.” 
' 14. Examination of Dove’s Theory of Lustre ; by Sir Davia Brew- 
SteR; (Proc. Brit. Assoc., Ath., No. 1300.)--The author explained the 
theory of Dove, which, if we took him correcily, was, that the lustre of 
les and particularly the metallic lustre arose from the light coming 
mM the one stratum of the superficial particles of bodies interfering on 
the eye with the light coming from other and deeper strata,—the regular 
Symmetrical arrangement of the particles in these bodies producing effect 
somewhat analogous to that of mother-of-pearl. But the opinion which 
Sir David himself seemed to incline to, was, that since we know from 
the phenomena of very thin metallic leaves. that lights of very different 
ista 
modate the eye to the distinct vision of these colors. He illustrated 
s by the effects produced when the two figures of a binocular stereo- 
Seope were colored with complementary colors, and viewed together in 
the instrument, 
g; 15. Notice of a Tree struck by Lightning Clandeboye Park; by 
Davin Brewster, (Proc. Brit. Assoc., Ath., No, 1300.)--The tree 
Stood inathick mass of wood, and was not the tallest of the group. The 
lightning bolt struck it laterally. about 15 feet above the ground, exactly 
atthe cleft where the two principal branches rose from the trunk. A 
large Part of the bark and a piece of the solid wood were driven to some 
Ce, and the electric fluid passed down the trunk into the ground, 
*plitting the tree in two by a rent through the whole of its thickness. The 
sats? by. conductor. ion of buildings from this 
‘Speci | s, and. that the protection of buildings } 
all iS Of meteor can only be effected by conductors stretching out in 
directions 
