to the electrodes 14 and 15 via connections 19 and 20 it should be noted here that in certain circumstances where the intensity of illumination on said photocell would reach an insufficient level e g due to poor illumination or to particular climatic conditions the energy gained from such a photocell of relatively limited size may be too low in such case it is advantageous to use the whole surface or at least part of the whole surface of the outer glass sheet 2 as a support for the photocell layer said layer not shown being then via conductors not shown printed on the glass sheet connected with the respective electrodes of the electrolysis cell in the cartridge fig2 shows another embodiment of a dehumidifying device according to the invention in analogy with fig1 neither the window frame nor the hinges or the means for securing the two glass sheets together are shown in fig2 in one glass sheet e g glass sheet 22 which is assumed to be the external glass sheet a preferably circular opening 24 has been made in which the dehumidifying cartridge is inserted this dehumidifying device comprises a glass container 25 which e g is shaped as a circular cylinder around the axis 0 0 this container is maintained in the opening 24 in the glass sheet 22 by means of a sleeve 26 of plastic or elastomer shaped with a cylindrical part 27 to be inserted in the opening 24 and with an external annular flange 28 to be located against the outer face of the glass sheet 22 around the opening and with an internal annular flange 29 surrounding the central opening 30 of the sleeve and forming a supporting edge for the glass.