1 76 Dr. Draper's Note on the Tithonotype. 



in the reversal that takes place. The right side of the tithono- 

 type corresponds to the right side of the original object, and 

 the left to the left. In the Daguerreotype it is not so. 



Copper tithonotypes were first made in this city by Mr. 

 Endicott, a lithographic artist of distinction. 



There is no great difficulty in obtaining from these titho- 

 notypes duplicate copies. An expert artist can multiply them 

 from one another. 



The problem of multiplying the beautiful productions of 

 M. Daguerre is therefore solved. 



I will take this opportunity of making a remark which I 

 intended to have inserted in my paper " On the rapid De- 

 tithonizing Power of certain Gases and Vapours," inserted in 

 the March Number of this Journal (S. 3. vol. xxii.). Ama- 

 teurs, in the Daguerreotype process, are often annoyed by the 

 want of success which frequently attends them. They ascribe 

 to the atmosphere, or to the light, or to other causes, their in- 

 ability to obtain impressions. Most of these mischances are 

 due to the accidental presence of the vapour of iodine, or other 

 electro-negative bodies, in the chamber or about the apparatus. 

 It is incredible what a brief exposure to these vapours will en- 

 tirely destroy a picture before it is mercurialized. If the 

 iodine box or the bromine bottle is kept in the same room with 

 the mercury apparatus, that circumstance in itself is often 

 sufficient to ensure an uniform want of success. If the little 

 frame which fits into the back of the camera, and which holds 

 the silver plate, be used in the iodizing process, as is often the 

 case, the small quantity of vapour it absorbs will destroy every 

 picture, or at all events increase the time required in the 

 camera enormously. The reason of this is easily understood. 

 Suppose a plate, in such a frame, be placed in the camera, or 

 what comes to the same thing, suppose a particle of iodine 

 has fallen into the camera, or that the wood has in any way 

 absorbed an electro-negative vapour ; as fast as the light makes 

 its impression on the sensitive surface the vapour detithonizes 

 it, and unless the light is quite intense or the exposure much 

 prolonged, a very feeble proof, or no proof at all, will be ob- 

 tained. In the same way the difficulties are greatly increased 

 in the process of mercurialization, for the temperature resorted 

 to being high, if there is the least particle of iodine about the 

 box, the picture will be inevitably and instantly detithonized 

 and ruined. 



We ought therefore never to allow iodine, or bromine, or 

 chlorine, to have access to the apartment or the apparatus in 

 which Daguerreotype operations are being conducted. 



University of New York, May 20, 1843. 



