21 Dr. Schoiiboin on the various Condiiwns of Oaijycn. 



it is easy to find theoretically that a double telescope whose optic 

 axes are parallel, and exactly the distance of the two eyes of the 

 observer from each other, and which magnifies n times, causes 

 objects so to appear as if all dimensions perpendicular to the axis 

 of the telescope remained unchanged, while the distance of the 



objects from the observer in the line of the axis is reduced -th, 



so that the observer sees the objects in their natural size, but 

 nearer, and compressed in the direction of depth. 



\Vhile each single telescope shows this object as if it were at 



- th of the distance, the difference between the perspective view 



n 



is still not so great as it would be if the observer actually saw the 



object at the -thof the distance. By combining a double telescope 



with a telostereoscope, this error is not removed; -we only obtain 

 a uniform further reduction of all apparent linear dimensions as 

 they appear in the double telescope. Of single objects, indeed, 

 which stand at a definite distance, a correct relief can be obtained 

 bv permitting the small reflectors to remain at an angle of 45°, 

 and making the large ones reflect at an angle somewhat smaller 

 than 4'5°. In this way, as before mentioned, an exaggerated 

 i-elief is obtained in the telestereoscope alone, and we can thereby 

 neutralize the opposite error of the telescopic combination. 



III. On the various Conditions of Oxygen. 

 By Dr. Sciionbein*. 

 My dear Faraday, l^isle, Sept. 17, 1857. 



IllAA'^E continued my researches on oxygen, that inexhaust- 

 ible source of investigation, and have become acquainted 

 with a series of novel facts, which seem to be not altogether void of 

 scientific interest. One of those facts is singular and ])aradoxical 

 enough. What do you say to a deoxidation of an oxygen com- 

 pound being effected by means of oxygen itself? You are per- 

 haps aware, that some years ago I found out a number of sub- 

 stances which possessed the power of transforming free O into 

 O, i. e. of acting like heat. The oxides of the precious metals, 

 and the metallic peroxides, such as those of manganese, lead, &c., 

 belong to this category, and are oxy-compounds which contain 

 either the whole or part of their oxygen in the ozonic condition. 

 Now it appears that the action which takes place, for instance 

 between free and PbO + 0, is reciprocal ; for not only is the 

 former converted into 0, but the peroxide of lead is at the sanu- 

 time reduced to PbO, thus appearing to show that the O of 

 * Coiiiiniiiiifiiteil bv Professor FaiMdjiv. 



