﻿Prof. P. Guthrie on the Thermal Resistance of Liquids. 469 



lower i rjTn\ f0r , the .I ,ro l uctioa of the first heat-effect in the 

 bv the t!' ^ ? ^ S 5°T S the smallne ^«f the difference caused 

 by the introduction of athermanous disks), and from comparison 



^ KfSrf °h, M ; S T' th , St Ae ^ °f-diaTion ui P aUU e 

 cases tried is negligible if not nothing 



By measuring resistance rather than conductivity, several sources 

 kfo icTT Dta l err0 '' T eliminated - W the two cones are broTh 

 zitn t l\r a t' ?, nd Wat6r ° f a kn0wn temperature is led for a 

 tuZt fthh 0USh Ule ?/f C ° ne > a certain dermal effect is pro! 

 duced in the lower one. If the cones be then separated, and a liouid 



b for Tied ffTr them> aDd lf W3ter ° fthe " ame temperatuT s 

 before be led for the same time as before through the upper cone 



effects %s a measure of the resistance of the liquid. Results so ob 



u the loTer cnn e e C ° rreC , ed *j ^ ?« ^'sure to which the a r 

 T„ fi VT f f IS sub J ect ^ as the water in the glass tube sinks 



account t f" 1 ? T? in the ™ al UMts ' we haTO to ^"t°* 

 account the diameter of the surface of the lower cone its capacit- 

 ance specific heat of the air which is in it. ' P J ' 

 I he following are the chief results obtained :— 



and tL Hl C ° nneX10 ^i n th , 6 i 'i StanCe of water ' bet ween the thickness 

 ?owi£ re( J u "' ed for the first heat-effect. 



forthe faheTI^'r ^ tem P ei ' a t«eand the time required 

 better than hea '" effect , ^ * shown that hotter water conducts heat 



» ivL^ 6 COnn fj on bet y eu the entire quantity of heat passing in 



water thlCkn6SS and temperature of the couduetnig- 



(4) The effect of the solution of various salts in altering tl,» 



Ssi: St of water > t ery sait «* - fo-d wZ £ 



mits that The eff ♦ T^Tr "", *? mal ««*■»»■ The author sub- 

 mits that the effect of the dissolved salt is chiefly, perhaps wholly due 

 to the displacement of a portion of the water by a subs ance ha'vin^ 

 greater resistance and to the modification in the^pecific heat of h? 

 liquid caused by the introduction of the salt 



(o) The resistance of the liquids in the following list was ex 

 amined under precisely similar circumstances. The ti'icknlss was 



2Vl7 C C T LT° r The initial temperature of the tq rid w 

 20 17 C, and the temperature-difference, AT, was 10°C. That is 

 the platinum surface of the upper cone was maintained at 30° 17C 

 The duration of the _ experiment in each case was I'. The numbers 



he r^ T^ "T^ ^ * e abore c™«">stances-tTat i™ 

 the ratio between the quantities of heat arrested by the severs 

 liquids and that arrested by water. V 



Phil. Mag. S. 4. Vol. 37. No. 251 . June 1869. 2 I 



