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XLIV. On the so-called Calorotypes, isoitli Animadversions on 

 the Papers of Mr. Hunt and Prof. Draper lately published in 

 the Philosophical Magazine. By Prof. Ludwig Moser'*. 



WAS not a little surprised to find in vol. lviii. of these 

 ■*• Annalen, an article by Mr. Robert Huntf of Falmouth 

 on Thermography, and one on Calorotypes by M. Knorr, in 

 which are communicated as discoveries facts which I had 

 previously described at length in the same work. Mr. Hunt 

 sets out from my first Memoir on Vision J, in which I demon- 

 strated the existence of invisible light; he repeats the experi- 

 ments which he read § in this Memoir, and gives them out as 

 his own discovery. I cannot name a single experiment com- 

 municated by either of the authors which I had not previously 

 described, except it be that the one employs a jasper instead 

 of an agate, which I used, or a bronze medallion instead of a 

 piece of copper coin. 



In my Memoir on Vision, &c. of May 1842 (vol. lvi. of 

 these Annalen), I communicated at page 206 [Sclent. Mem. 

 vol. iii. p. 43] the fact, that when any body is warmed it depicts 

 itself on metallic or glass plates ; that the same also occurs 

 when the plate is warmed instead of the body. These expe- 

 riments led me at first to believe that heat had some part in 

 the production of these images, and Mr. Hunt, as also M. 

 Knorr, who have repeated them, have stopt short at this 

 erroneous view. Not so with me ; for the following page de- 

 scribed the same experiment made without the intervention 

 of any artificial temperature, adding the following observa- 

 tions: — 



"The action of light wa3 therefore imitated and extended by my expe- 

 riments; and indeed, as it appeared, by the employment of unequal tem- 

 peratures. But this latter view could not possibly be long entertained ; 

 it is only necessary to observe one of the above-described images, if well 

 executed, in order to be convinced that such representations, in which the 

 finest lines of the original may often be traced, could not possibly be pro- 

 duced by differences of temperature, more particularly on a thin, well- 

 conducting plate of metal. Moreover, the variety of the substances em- 



* From PoggendorfF's Annalen, vol. lix. part 1. Translated and com- 

 municated by William Francis, Ph.D. 



f The paper referred to is a translation of Art. LXXXI. in the Phil. 

 Mag. for Dec. 1842.— Edit. 



% A translation of the whole of this Memoir, and also of those on Latent 

 Light and on Invisible Light, by M. Moser, were published in Part XL of 

 Taylor's Scientific Memoirs, in Feb. 1843. 



§ Mr. Hunt's paper, as just intimated, appeared in the Philosophical 

 Magazine for December 1842. The first and very imperfect notice in this 

 country of M. Moser's investigations was communicated at the Meeting of 

 the British Association in June of the same year. It related solely to ex- 

 periments and views detailed in the first of the three Memoirs. — Edit, 



