336 
ME. WAEEEN DE LA EUE ON THE 
Originally, merely a temporary tent in which to develope the photographs was procm:ed ; 
but when it was known that H.M.S. ‘Himalaya’ would be placed at the disposal of 
the Astronomer Royal, I put this aside, and caused a complete photographic obseiwatory 
to be constructed, part to contain the heliograph with a removable roof, and part divided 
off and fitted up as a photographic room, with a cistern, to be filled from the outside, a 
sink, and with tables and shelves to hold the apparatus and photographs. This obser- 
vatory took to pieces, and every part was marked when in its place, so that no time 
need be lost in putting it together again in its destined position. Besides the ordinary 
roof, there was another covering, consisting of strong canvas, supported at the distance 
of about three feet from the walls and roof of the developing-room. The object of this 
was to prevent the overheating of the photographic room, a circumstance most detri- 
mental to photography. This canvas was kept wetted with water, in order that the 
evaporation might lower the temperature of the stratum of air between it and the 
observatory, and it fulfilled the object perfectly. The canvas, when the observatory was 
not in use, was drawn over the room containing the heliograph, and protected the 
instrument from rain. 
