152 Intelligence and Miscellaneous Articles. 



The pseudoscope being directed to an object, and adjusted so that 

 the object shall appear of its proper size and at its usual distance, 

 the distances of all other objects are inverted ; all nearer objects ap- 

 pear more distant, and all more distant objects nearer. The con- 

 version of relief of an object consists in the transposition of the 

 distances of the points which compose it. With the pseudoscope 

 we have a glance, as it were, into another visible world, in which 

 external objects and our internal perceptions have no longer their 

 habitual relations with each other. Among the remarkable illusions 

 it occasions, the following were mentioned. The inside of a tea- 

 cup appears a solid convex body ; the effect is more striking if there 

 are painted figures within the cup. A china vase, ornamented with 

 coloured flowers in relief, appears to be a vertical section of the in- 

 terior of the vase, with painted hollow impressions of the flowers. 

 A small terrestrial globe appears a concave hemisphere ; when the 

 globe is turned on its axis, the appearance and disappearance of 

 different portions of the map on its concave surface has a very sin- 

 gular effect. A bust regarded in front becomes a deep hollow 

 mask ; when regarded en profile, the appearance is equally striking. 

 A framed picture, hung against a wall, appears as if imbedded in a 

 cavity made in the wall. An object placed before the wall of a room 

 appears behind the wall, and as if an aperture of the proper dimen- 

 sions had been made to allow it to be seen ; if the object be illumi- 

 nated by a candle, its shadow appears as far before the object as it 

 actually is behind it. 



The communication concludes with a variety of details relating to 

 the conditions on which these phenomena depend, and with a de- 

 scription of some other methods of producing the pseudoscopic 

 appearances. 



XXV. Intelligence and Miscellaneous Articles. 



ON M. GILLARD's LIGHT FOR ILLUMINATION OBTAINED FROM 

 THE BURNING OF HYDROGEN. BY B. S1LLIMAN, JUN. 



WE have had an opportunity of seeing the successful application of 

 M.Gillard's patent in the extensive silver plate works of Messrs. 

 Christolef in Paris. It is well known that M. Gillard claims the pro- 

 duction of a useful light and great heat from the combustion of hy- 

 drogen in contact with a coil of platinum wire, the hydrogen being 

 produced by the decomposition of water. The apparatus employed 

 is very simple, and consists essentially of one or more cylinders of 

 iron arranged horizontally in a furnace similar in all respects to the 

 usual arrangement for the production of coal-gas. The retorts are 

 charged with wood-charcoal reduced to small fragments of uniform 

 size and heated to an intense degree. Through each of the retorts 

 steam is conducted in a tube pierced with numerous very minute 

 holes so disposed as to distribute the steam in a uniform and very 

 gradual manner over the heated coal. The boiler for the production 



