KEW OBSERVATORY AND METEOROLOGY 235 



compendious yearly volume. If so, the tracings 

 would require very much more reduction in breadth 

 than in height, for the photographic mark made by 

 the recorder was so broad that the scale of the tracing 

 had to be proportionately wide open ; otherwise the 

 neighbouring irregularities would blur together. A 

 sharp line drawn along the middle of the tracings 

 might, however, be much compressed laterally and yet 

 show all the irregularities distinctly. I designed a 

 compound drill pantagraph for the purpose, which 

 reduced the tracings in height independently of the 

 reduction in length. One part of the machine worked 

 the drill forward and backwards, the other part moved 

 the plate from side to side upon which it worked. 

 The result was to express the tracings by fine 

 grooves cut into a piece of soft metal. These were 

 again reduced by an ordinary pantagraph. The 

 whole process required thinking out in numerous 

 details, but it proved quite a success. It is described 

 in the annual Report of the Meteorological Office for 

 1869. 



Squares of zinc, one for each day, were grooved 

 by the drill pantagraph so as to show every one of 

 the data without confusion. They referred to Wind 

 Velocity and Direction, Barometric Height, Rainfall, 

 Dry and Wet Thermometer, together with a line to 

 show the amount of Humidity in the air, which was 

 mechanically calculated from the combined traces of 

 the two thermometers. These squares were placed 

 beneath a large and beautifully designed German 

 pantagraph, whose pointer was directed along the 

 grooves in the zinc, while the diamond point of the 

 scribe scratched the varnish on a copper plate, which 



