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VIII. On the Insulation of Highly Attenuated Wires in Pla- 

 tinum Resistance Thermometers. By J. J. Manley, M.A., 



Research Fellow, Magdalen College, Oxford*. 



rrHE construction of platinum thermometers having bulbs 

 JL with a diameter of 2 mm. and resistance wires the 

 thinness of which ranges from *06 to *02 mm., presents some 

 difficulties of an exceptional order. Of these the greatest is 

 probably that encountered when we proceed to support and 

 insulate the highly attenuated wire. The cross frame of mica 

 introduced by Griffiths, being from lack of space inadmissible, 

 the difficulty can only be surmounted by having recourse to 

 other methods. By trial it was ultimately found that in 

 addition to the plan first described by Burstall f and sub- 

 sequently bv.Callendar and Nicholson J three others were 

 available : these we now briefly describe. 



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1. In all cases where a resistance of from 3 to 5 ohms 

 suffices, BurstalFs simple plan may with advantage be 

 followed, the wire being arranged as a loop as shown in 

 fig. a. Placed in situ, much of the loop makes contact with 

 the containing tube : this is helpful, for the thermometer is 

 thereby enabled all the more readily to acquire the tempe- 

 rature of the surrounding medium. If the loop is well 



* Communicated by the Author, 

 t Phil Mag. Oct. 1695. 

 t Proc. lust. C. E. 1893. 



