477 
of Edinburgh , Session 1868-69. 
The following Communications were read : — 
1. Practical Note on Intensified Gravity in Centrifugal 
Governors. By Professor C. Piazzi Smyth. 
This paper, after a short introduction upon previous publications 
and experiences, describes in a plain and practical manner four 
steps of improvement recently made in the centrifugal governor of 
an equatorial driving clock ; and touches on 
1. The number of the pendulums ; 
2. Their weight and momentum ; 
3. Their chronometric principle ; and 
4. The intensification of the effect of gravity upon them, 
chiefly to increase the promptitude and energy of the 
centrifugal action. 
This last improvement the author regards as the most important 
to draw attention to, because it is capable of imparting extreme 
quickness and sensibility to the actions of all kinds of centrifugal 
governors ; and although not absolutely new, it does not seem 
yet to be sufficiently known or employed in many practical cases, 
where it might be of the utmost use, as in preventing some classes 
of disasters which are in these days happening far too frequently 
to sea-going screw-steamers. 
The paper has since been printed in full in the “ Practical 
Mechanic’s Journal ” for March 1, 1869. 
2. Mr Mills Theory of Geometrical Reasoning Mathemati- 
cally Tested. By W. R. Smith, Esq., Assistant to the 
Professor of Natural Philosophy. Communicated by 
Professor Tait. 
An amusing and instructive example of the way in which logicians 
are accustomed to dogmatise upon the theory of sciences that they 
do not understand, is afforded by Mr Mill’s explanation of the 
nature of geometrical reasoning. 
Those who remember that Mr Mill assures Dr Whewell that he 
has conscientiously studied geometry (Logic, 7th ed. I. 270), will 
probably find some difficulty in believing that the demonstration of 
Euc. I 5 , which Mr Mill offers as an illustration of the justice of his 
3 Q 
vol. VJ. 
