154 



Projection Apparatus and Accessories. 



The optical bench can easily be removed by loosening two nuts, and it is therefore possible 

 when necessary to set up independent instruments, etc. in front of the lantern. 



The cooling chamber listed on the table of prices on p. 161 (see also Fig. No. 50,796/50,767. 

 p. 163) is filled with water, or, better still, with a solution of ferrous ammonium oxide, which absorbs 

 the heat well. For protracted working of the projector a cooling chamber (Xos. 50,976 or 50.977) is 

 suitable, this being placed on the optical bench in front of the condenser. 



With regard to the individual outfits and optical installations of various pi-ices, reference should 

 be made to the price list. 



Directions to be observed for the Attention of the Lamps. 



Attention of Arc Lamps. An important condition to be observed if a light of the maximum 

 brilliancy is to be derived, is the correct adjustment of the carbons. Before inserting fresh carbons, the 

 carbon holders should be separated to such extent that the new carbons when fitted 

 are a few millimetres apart; the thicker -- the cored carbon -- is placed in the upper 

 carbon holder in the case of Direct Current lamps. The freshly inserted carbons should 

 be of equal length. In the vertically arranged lamp of the Type B projector the lower 

 carbon should be so adjusted that it inclines slightly towards the condenser, as shown 

 in Fig, 50,728 C. The most favourable degree of brilliancy in proportion to the current 

 consumed will then be attained. The action is secured in that with this arrangement 

 a lateral crater of light forms in the upper carbon, emitting its brilliant rays in the 

 direction of projection. In the case of the other arc light regulators included in the 

 list the same action is produced to a lesser or greater degree by tilting the carbons 

 in various ways (cf. the Price List). The point of illumination must be in the optical 

 axis of the lantern, this being secured by raising and lowering the lamp. 



50 728 C. 



An eye must be kept upon the correct distance and adjustment of the carbons, and care taken 

 to see that they burn correctly. The distance apart of the carbons must not be too small, not under 

 2 mm, so as not to cause too great an increase of current, which may cause the fuses to blow or set 

 up heating in the conductors. The illustration (Fig. 50,729A) shows the correct formation of the crater 

 for the carbons of the direct current arc lamp. Fig. 50,729 B shows an arboreous formation which makes 

 its appearance on the negative carbon when the carbons are too close together, and which easily gives 



50729. 



rise to faults in working; this defect should be remedied as soon as it observed. Fig. 50 729 C shows 

 the shape of the arc when the carbons are too far apart, while Fig. 50,729 D shows the shape assumed 

 by the tips of the carbons when the lamps are burning with the current reversed. In the latter case 

 the leads should be changed round. The illustrations here reproduced are taken from Hassack and 

 Rosenberg's work entitled ,,Die Projektionsapparate", Vienna and Leipzig. 1907. 



In the case of those lanterns in which the distance of the arc lamp from the condenser is in- 

 variable (Model B, Schuckert type) the correct relative distance between these two portions of the 

 projector are given to the apparatus in the manufacture in order that clear images may result. When 

 the arc lamp is made adjustable, the following operation should be observed: An image should be placed 

 in front of the condenser and sharply focussed on to the screen by sliding the objective. The picture 

 should then be removed and the arc lamp moved until the whole projection surface is evenly lighted 

 and surrounded by a sharp border. After replacing the picture in front of the condenser, it should again 

 be sharply focussed. 



The correct position of the source of illumination in relation to the condenser can be deter- 

 mined by projecting the circle of light on to the screen before introducing the object which it is de- 

 sired to project. From the nature of this light image (according as it is equally bright or partly clouded) 

 it is possible to decide as to the position of the centre of illumination. The sketch (Fig. 50,729 E) 

 appended shows the influence of the relative positions of condenser and source of light on the 

 light-image. 



Cl. 244, 9F, 10 F. 



