12 REroRT — 1844. 



showed no expansion, and consequently received no accession of caloric. By in- 

 creasing the force of the battery beyond a certain point, the thermometer does acquire 

 heat and show expansion of its included mercury, but still the expansion of the 

 mercury in which it is plunged proceeds in a greater degree, and remains five or six 

 degrees in advance. Various other considerations are presented, from which the 

 author concludes, that the existences already named are but varied forms of one fluid, 

 and that caloric in a state of repose is the universal, latent, and primitive fluid of 

 all undisturbed matter. 



0?t n new Process of Magnetic Manipulation, and its Action on Cast Iron and 

 Steel Bars. By the Rev. William Scoresby, D.D., F.R.S. L. S^ E. 



Dr. Scoresby found that it was impossible, by the ordinary process, to communicate 

 the full charge of magnetic influence to hard thin bars of steel of the horse-shoe 

 form. Nor was it practicable to magnetize fully thin plates or bars of a straight or 

 ruler form, with a horse-shoe magnet, by the usual processes of manipulation, pro- 

 vided the bars were very hard, or such as were best suited for retaining the magnetic 

 energy, and therefore best for the manufacture of magnets. But he was led, by the 

 theoretic views he holds, to try the effect of interposing thin bars of soft iron between 

 the charging poles of the magnet and the steel bar to be magnetized ; this answered 

 effectually, and Dr. Scoresby exhibited to the Section several experiments, whereby, 

 with the old process, the magnetism imparted to the steel bars was very trivial, but 

 by the adoption of the new process, a remarkably strong charge was communicated 

 by one single stroke of the poles of the magnet over the bar, whether of steel or cast 

 iron. And it was stated that such was the eflicacy of the process on bars of cast 

 iron, either with an interposed malleable or cast iron bar, that one such cast iron bar 

 received a power of sustaining about tw^elve pounds. 



On a new Steering and Azimuth Compass. By E. J. Dent, F.R.A.S. 



Contributions to Actino- Chemistry. On the Amphitype, a new Photographic 



Process. 

 By Sir John F. W. Herschel, Bart., F.R.S. L.^E., Hon. M.R.I.A. 



At the end of my paper ' On the Action of the Solar Spectrum on Vegetable 

 Colours,' communicated to the Royal Society in 1842, a process is alluded to (in 

 Art. 230), by which positive pictures are obtained, having a perfect resemblance to 

 impressions of engravings taken with common printers' ink. I had hoped speedily 

 to have perfected this process so far as to have reduced it to a definite statement of 

 manipulations which would ensure success. But, capricious as photographic pro- 

 cesses notoriously are, this has proved so beyond even the ordinary measure of such 

 caprice ; and, having of late been able to give little or no time to this pursuit, I have 

 thought it preferable to describe the process in a general way, and in a form in which 

 I have found it frequently, and sometimes eminently successful ; not so much for 

 the sake of its results, which yet are not wanting in interest or beauty, as for the 

 curious and very complicated photographic habitudes of iron, mercury, and lead 

 which are concerned in their production, — rather, in short, as a contribution to the 

 newly-created science of actino- chemistry, than to the photographic art. Paper 

 proper for producing an amphitype picture may be prepared either with the ferro- 

 tartrate or the ferro-citrate of the protoxide or the peroxide of mercury, or of the 

 protoxide of lead, by using creams of these salts, or by successive applications of 

 the nitrates of the respective oxides, singly or in mixture, to the paper, alternating 

 with solutions of the ammonio-tartrate or ammonio-citrate of iron*, the latter solu- 

 tions being last applied, and in more or less excess. I purposely avoid stating pro- 

 portions, as I have not yet been able to fix upon any which certainly succeed. 

 Paper so prepared and dried takes a negative picture, in a time varying from half an 

 hour to five or six hours, according to the intensity of the light ; and the impression 

 produced varies in apparent force from a faint and hardly perceptible picture, to one 



* So commonly called, and sold as such ; but as I am disposed to regard their composition, 

 their chemical names would be ferro-tartrate and ferro-citrate of ammonia. 



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