488 Dr. A. Downes and Mr. T.. P. Blunt on [Dec. 6, 



called a precipice, with a fall of about a thousand feet. A gentle breeze 

 was blowing from the mountains, which were partly snow-covered, and 

 partly of bare rock, towards the precipice. Taking care to cleanse my 

 pliers in the flame of a spirit-lamp, and to keep my body to leeward of 

 the flasks, I snipped off their sealed ends. 



The two groups of flasks were then placed in our own little kitchen, 

 where the temperature varied from about 65° to 90° Fahrenheit. 



Result : — Twenty- one of the twenty-three flasks opened on the hay-loft 

 are filled with organisms ; two of them remain clear. 



All the flasks opened on the edge of the precipice remain as clear as 

 distilled water. Not one of them has given way. 



This is a striking confirmation of the experiments of Pasteur upon the 

 Mer de Grlace. 



Ever, my dear Huxley, 



Tours faithfully, 



John Tyndall. 



III. " Researches on the Effect of Light upon Bacteria and other 

 Organisms." By Arthur Downes, M.D., S.Sc. Cert. Cantab., 

 and Thos. P. Blunt, M.A. (Oxon.), E.C.S. Communicated 

 by J. Marshall, F.R.S., Professor of Anatomy to the Royal 

 Academy of Arts. Received October 18, 1877. 



The investigation to which the following communication relates was 

 undertaken by us with the view of ascertaining, first, whether light could 

 be shown to exert any appreciable influence, favourable or the reverse, 

 upon the development of Bacteria and other organisms in certain of those 

 solutions which afford a suitable medium for their appearance and 

 increase. 



We feel justified in thus presenting our earlier researches and the 

 conclusions drawn from them, by considering that every fact, however 

 small, which tends to throw light upon the life-history of these organisms 

 is of importance as bearing upon questions of the highest moment and 

 most varied interest. 



In the experiments about to be recorded the contents of the tubes were 

 in most cases examined under a high power, and the turbidity, when such 

 occurred, was invariably found to be occasioned by swarms of Bacteria. 

 The best index of the development of the Bacteria we found to be the 

 degree of turbidity and the time of its commencement. 



Obs. 1. April 24. — Eight ordinary thin test-tubes were cleansed with 

 strong sulphuric acid and thoroughly rinsed with tap-water. They were 

 then partially filled with freshly made unboiled Pasteur's solution, the 

 exact composition of which is given in the Appendix (A). Four of the 

 tubes were encased in thin sheet-lead so as entirely to exclude light, and 



