A NEW THERMOGRAPH. Patent ai.plled /or. 



The Thermographs hitherto in use consist of a compound bar composed of a strip of lirass or 

 zinc soldered to a similar piece of iron. The minute alteration in the curvature cf this bar caused by 

 variation of temperature is greatly magnified and made visible by a series of multiplying levers. 

 Any slight error in the curvature of tne bar is, therefore, greatly magnified in direct ratio to the 

 magnifying power of the levers. Errors constantly occur, especially with zinc, owing to its varying 

 expansibility under different conditions. Any method whereby these difficulties can be obviattd must 

 be a decided improvement. 



By using two substances of widely different co-efficients of expansion, a thermograph has been 

 made which gives sufficient direct movement without the use of levers or multiplying gear. Seveial 

 substances have been tried, but vulcanite or celluloid with nickel-steel or wood have proved most 

 satisfactory. Wood and nickel-steel both have low co-efficients of expansion, but the latter is better, 

 not being affected by moisture and being of a lower expansibility. 



Table of co-efficients of expansion : 



Nickel-steel 



Wood 



Iron 



From the above table it will be seen that the relative difference between iron and brass is as 2 to 

 3 between iron and zinc 1 to 2^, and between vulcanite and nickel-steel 1 to lOo. 



The instrument is now made with a compound bar of vulcanite and nickel-steel, and has a range 

 of nearly one inch for every IC^ F. It is supplied complete with clock and drum, the latter recording 

 continuously for a week without changing the chart. It has a setting screw by means of which the 

 recording pen can be brought to any mark on the chart, and the hour mark is brought under the 

 pen by setting the clock in the usual manner. 



This instrument is the simplest Thermograph made, and the least likely to get out of order, and 

 having no multiplying levers it is far more accurate and more sensitive. It can be made to fit inside 

 the Stevenson screen. 



Application fot a Provisional Patent has been made for most of these instruments and they are 

 protected throughout the principal Countries of the World. 



=^>rfaV=£. 



HYGROMETER AND RAIN GAUGE. 



The figures best explain these instruments. They are made to 

 record in the ordinary Stevenson screen. The rain gauge has a 

 tap near the bottom and when this is opened the pen sinks to the 

 bottom of thescale and this can be done as frequenty as dcsirtd 

 The funnel and tube can be surrounded with a water-jaclot through 

 which, in cold weather, a stream of water is passed from the 

 nearest water supply and this melts snow as it falls and prevents 

 the water freezing around the float. In the Stevenson screen at 

 Canterbury a belt around the Thermograph drum diives the drum 

 that records both humidity and rainfall. Thus one eight-day 

 clock is sufficient for the three records and it needs little attention 

 until the end of the week. 



