of Edinburgh, Session 1880-81. 
101 
intensely active mind found congenial occupation in scientific and 
literary pursuits. He discovered the peculiar effect of light on 
gelatine when treated with the bichromate of potash, which was 
afterwards practically applied in the autotype process. Indeed, it 
is upon the sensitiveness of this salt to light, under certain con- 
ditions, that all the processes of permanent printing of the present 
day are based ; and this discovery of his consequently marks the 
commencement of an era in photography, and renders his name as 
closely connected with the history of that art as are those of 
Niepce, Daguerre, and Talbot. It was in 1839— the very year in 
which the wonderful process of Daguerre was announced to the 
world — that Mungo Ponton called attention to bichromate of 
jS 
potash as a photographic agent, and described a process — the 
foundation of every subsequent permanent printing process — 
whereby, through that agent, durable impressions on paper might 
be produced. This discovery, which had been first announced to 
the Scottish Society of Arts on 29th May 1839, was given to the 
world in the Edinburgh New Philosophical Journal, vol. xxvii., 
1839, under the title, “Notice of a Cheap and Simple Method of 
Preparing Paper for Photographic Drawing.” 
In December 1838, he obtained the Honorary Silver Medal of 
the Society of Arts of Scotland, “ for the ingenuity displayed by 
him in the Model and Description of his Improved Electric Tele- 
graph ; read and exhibited 10th January and 20th June 1838, 
when Mr Ponton presented his elegant model to the Society, to be 
placed in their Museum.” 
His inventive turn of mind led him to take a great interest in the 
proceedings of the Scottish Society of Arts. He was admitted a 
Fellow of that Society in 1833, and shortly afterwards was made 
Foreign Secretary. He was elected their Vice-President in 1837, 
and again in 1844. He also acted for some time as editor of 
their Transactions. His first scientific paper, “ On a Method of 
increasing the Adhesion of the Wheels of Locomotives to the Kails ” 
was communicated to that Society in 1837. 
He was the first who employed the photographic method for 
registering automatically the fluctuations in thermometers and other 
instruments, and for this invention he received also the Silver 
Medal of the same Society in 1845. 
