6 Proceedings of Eoycd Society of Edinlurgh. [sess. 
tliis subject in coiinectiou with the keen and sometimes acrimonious 
discussion on spontaneous generation. True, then it was to the 
organised and living particles in the air that attention was directed, 
but it gave a great impetus to investigation of the whole question of 
aerial dust. The laborious work of Tissandier in Paris, of Angus 
Smith in this country, and of Fodor in Austro-Hungary, have given 
us some important knowledge of the amount and nature of those 
dust particles, but how rough even the most careful gravo-metric 
methods are vdien compared with that of Aitken ! How simple the 
manipulation, especially with the portable apparatus, which he 
described in his last communication to the Society ! One wonders 
whether the optically pure air of Tyndall would stand this test. 
As one interested in hygienic investigations, I should like to see it 
applied not only to enumerating the particles, but in showing how 
much is organic, and how much inorganic. Suppose the normal air 
of a room were examined, and then a sample of the same air pre- 
viously passed say through a red-hot tube to destroy organic matter, 
would this give us a means of determining the organic particles of 
the atmosphere ? It might be difficult of execution, but the results 
would be important. On the vexed question of ventilation I think 
it can throw much light. Indeed, by some of his experiments in 
this room and elsewhere, Mr Aitken has shown that with sufficient 
means of air renewal his instrument can readily detect rates of air 
purification. One cannot but feel that with this new aid many 
important points will be elucidated. 
It is my duty to make mention of those of our number who have 
passed away since the opening of last Session. These were fourteen 
Ordinary, and two Honorary Fellows. I would in no sense have it 
supposed that a short passing notice here, is to be regarded as any- 
thing else than a suggestion to others who may have special know- 
ledge, to give us better records of our deceased colleagues at the 
ordinary meetings of the Society. But in truth such suggestions 
are in great measure unnecessary now, as in a large proportion of 
those whom I have to name this has been anticipated by interesting 
memoirs read to the Society during last session. 
Of Professor Cosmo Innes Burton, the gifted " son of a 
gifted father, I would say no more than that an interesting notice, 
by Mr William Marshall of this young scientist who has been 
