Mr Ponton on Fhotoyraphic Druicing. 169 



to throw up the heel of the rudder, render it useless in steer- 

 ing the ship, and tear away the cumbrous apparatus of guys, 

 &c. usually led under the bottom of the ship with the inten- 

 tion of keeping the heel of the rudder down. But by the me- 

 thod I have now suggested, the rudder will be maintained 

 in a good position, and in perfect security. 



My plan is, as I have before said, cheap and simple, and it 

 will give me heartfelt satisfaction if thLs suggestion is ever 

 found useful in a time of need. 



Martyn J. Roberts. 



Notice of a cheap and simple metliod of preparing paper for 

 Photographic Drawing, in which the use of ang salt of silver 

 is dispensed with. By Mungo Ponton, Esq., F.R. S. E., 

 Foreign Secretary Society of Arts for Scotland. Commu- 

 nicated by the Society of Arts. " 



While attempting to prepare paper with the chromate of 

 silver, for which purpose 1 used first the chromate of potash, 

 and then the bichromate of that alkali ; I discovered that 

 Avhen paper was immersed in the bichromate of potash alone, 

 it was powerfully and rapidly acted on by the sun's rays. It 

 accordingly occurred to me, to try paper so prepared to obtam 

 drawings, though I did not at first see how they were to be 

 fixed. The result exceeded my expectations. When an ob- 

 ject is laid in the usual way on this paper, the portion exposed 

 to the light speedily becomes tawny, passing more or less into 

 a deep orange, according to the strength of the solution, and 

 the intensity of the light. The portion covered by the object 

 retains the original bright yellow tint, which it had before ex- 

 posure, and the object is thus represented yellow upon an 

 orange ground, there being several gradations of shade, or tint, 

 according to the greater or less degree of transparency in the 

 difi^erent parts of the object. 



In this state, of course, the drawing though very beautiful, 

 is evanescent. To fix it, all tb.nt is required is careful im- 

 mersion in water, ^vhen it will be found that those i)ortions of 



* Read bt-foiu tlie Society of Arts for Scotlaud '2'Jth JIny 1839. 



