Prof. Waltenhofen on an anomalous Magnetizing of Iron. 113 



of gases entered it ; therefore in about ten seconds its contents 

 were renewed. There was no absolute thermometer placed in it, 

 the air-thermometer employed for the observation of the rise of 

 temperature on the admission of the two gases being a purely 

 relative one. With gases rushing through it at the rate of 7 to 

 14 cubic centims. per second, it ceases to be certain whether the 

 temperature of the interior of the flask would be 350°. In short, 

 we neither know the temperature of the flask when the hydro- 

 chloric acid was rushing through it, nor when the mixed gases 

 were rushing through it — all that we know being that the latter 

 temperature was sensibly higher than the former. 



Turning next to Thanhs very ingenious modification of the ex- 

 periment*, it appears to me to be certain that the amount of heat 

 produced by anything approaching to complete combination 

 between the acid and ammonia must have been abundantly indi- 

 cated by his apparatus. It is quite true that the kind of air- 

 thermometer employed was not calculated to indicate slight 

 alterations of temperature; but a change of much less than 

 40° C. (the rise of temperature in M. DevihVs former experi- 

 ment) could not possibly have failed to give a decisive indication. 



M. Deville's objection that Thanhs gases were at rest when 

 they came together is without foundation. Inasmuch as Than 

 broke the inner vessel (about the upper third) by striking it 

 violently against the top of his graduated tube, it will be mani- 

 fest that the gases were in movement when they came together ; 

 and inasmuch as the hydrochloric acid was discharged at the top 

 of the tube, the fact of its being of higher specific gravity than 

 the ammonia would be in Thau's favour — not against him, as 

 M. Deville argues. 



London Institution, 

 January 12, 1865. 



XIX. On an anomalous Magnetizing of Iron. 

 By Prof. A. von Waltenhofen of Innsbruck-^. 



IN the criticism of the hypotheses of natural science, those 

 facts are especially decisive which not only lend support to 

 one of the conflicting theories, but at the same time take it from 

 another. If the discussion relate to the theory of molecular mag- 

 netism as opposed to the theory of the two fluids, there is no lack 

 of facts in favour of the former and in opposition to the latter. 

 To these belong in an especial manner the alterations in the 



* Ann. der Chem. und Pharm. August 1864. 



t Translated by Prof. Wanklyn from the Berichte der Wiener Alcademie 

 der Wessenschaften. 



Phil. Mag. S. 4. Vol. 29. No. 194. Feb. 1865. I 



