795 



The core A possesses a somewhat (hiiiuoi- wall at (/. and is conical 

 excavated on the lathe, as indicated in the iignre J, with the purpose 

 to give the rather strongly deviating R(")NT(iKN-rays an opportunity 

 to reach the photogra[)hic plate without an interposing obstacle. The 

 furnace-chamber must be kepi at a constant temperature however ; 

 therefore it is necessary, to shut it at ^f, and like-wise the cover 

 Q^, to protect the photogra})hic plate from heat-radiation, at N^ 

 by means of a thin plate of aluminium, which can be (ixed or 

 removed by means of a copper-ring. In this way the heat is 

 sufficiently kept in the chamber, while the aluminium-screens do not 

 interpose any appi-eciable obstacle in the way of the RöNTGKN-rays. 

 The aluminium screens have, at o, only a hole to introduce the 

 thermoelement Th into the furnace. The crystal-plate p to be inves- 

 tigated, is fixed in positioii on a removable support, which can be 

 adjusted in the furnace-chamber l^y means of the buttons m^ and 

 m^, and a bayonet-joint under the screws .Vi and s,, The crystal 

 is fixed on the support l\y means of the two metal springs ^j and y.^. 

 The furnace-coil can bear a maximum current of 5,5 Amperes ; with 

 this intensity a temperature of 800° C. or somewhat higher, can be 

 reached. 



The connection of the furnace with the RöNTGEN-apparatus was 

 made in the following way. A brass plate was fixed in a xertical 

 position on a long horizontal rail ; against the vertical end of the 

 plate a heavy lead-screen was fixed. In the brass plate a long brass 

 tube of about 7 cm. is fixed, and adjusted in a horizontal position; 

 this tube bears at the side where the furnace stands, (i. e. at this 

 side of the lead screen), a brass flange, which is turned off on the 

 lathe in such a way, that the plane of its border is accurately adjusted 

 perpendicularly to the direction of the emerging RöNTGEN-rays. The 

 tube R of the furnace just encircles the border of this flange. In 

 the brass tube two cylinders of lead, about 5 m.m. long, are arranged 

 at both terminals ; they are fixed in such a way, that no rays can 

 escape otherwise, than through the 1 m.m. broad central canals, 

 which are pierced along the axes of the lead cylinders. As they are 

 accurately adjusted so, that the axes of the two cylinders are 

 lying in the same straight line, the direction of the bundle of Röntgen- 

 rays fabout 1 m.m. in diameter) is wholly determined, as it were 

 by means of a visor. Everywhere thick lead-i)lates are ari-anged so 

 as to prevent the RöNTGEN-ways from escaping otherwise, than 

 through the narrow canal. 



The furnace, with its axis in horizontal position, is now connected 

 with the RöNTGEN-apparatus, by pushing the lube R over the liange; 



