IV. On the Automatic Registration of Magnetometers, and Meteorological Instru- 
ments, by Photography. — No. III. By Charles Brooke^ M.B., F.R.S. 
Received June 21, — Read June 21, 1849. 
On the Construction of the Self registering Thermometer Apparatus. 
In my second paper on Automatic Registration*, the means of obtaining a photo- 
graphic register of the variations of the thermometer were briefly mentioned, and in 
the annexed plate a specimen was given of the register thus obtained ; but as an ap- 
paratus possessing the requisites for practical application had not then been con- 
structed, it may not be undesirable to those who are interested in the advancement 
of meteorological science, to know the means by which this object has been accom- 
plished. A vertical revolving cylinder, and the carrying time-piece described in the 
above paper (see Plate VI. figs. 4, 5, 6, 7, 8), are mounted on a stand measuring 30 
inches by 12, supported by four legs ; the stems of the thermometer and psychrometer 
pass up through the table, and between the lenses and the adjacent surfaces of the 
cylinder ; and the long cylindrical bulbs are sufficiently below the stand to be freely 
influenced by the currents of air, and at the same time to remain wholly unaffected 
by the heat of the lamps which are placed on wooden supports at each end of the 
stand, at such a height that the flame may be opposite the middle of the photographic 
paper on the cylinder. 
As it is impossible to superpose two registers of these instruments on the same 
paper, which may be done without inconvenience when the indication consists in a 
dark line, as in the photographs of the barometer and the magnetometers, the time- 
piece is so constructed that the hour-hand makes half a revolution in twenty-four 
hours. By this arrangement the two halves of the paper surrounding the cylinder 
give respectively a perfect diary of the two instruments. The glass cylinder is covered 
by a concentric cylindrical zinc case, having slits on opposite sides corresponding* 
to the stems of the instruments, which are capable of being closed by sliding doors ; 
by these means the cylinder, protected by its case, may be carried to or from the 
room in which the photographic manipulations are conducted, without any risk of 
exposure to light. The whole apparatus is also covered by a wind- and water-tight 
zinc case which rests on the stand, and is divided into separate compartments for 
the lamps by a partition towards each end, for the purpose of more completely 
isolating the thermometers from the heat produced by their combustion. 
The cylindrical arrangement above described, so obviously desirable in enabling 
* See Philosophical Transactions, 1847, Part I. 
