286 Thermal Conductivities of Single and Mixed Solids, fyc. 



spores in cultures, and Basidiomycetes generally have rarely been 

 made to do so. 



The actions of the mycelium on the wood of JEsculus, Pinus, 

 Quercus, and Salix are also examined, and this is, so far as known, 

 the first time this has been done with pure cultures. 



Anatomical and histological details, with figures, are given in the 

 complete paper. 



" On the Thermal Conductivities of Single and Mixed Solids and 

 Liquids, and their Variation with Temperature." By 

 Charles H. Lees, D.Sc., Assistant Lecturer in Physics in 

 the Owens College. Communicated by Professor SCHUSTER, 

 F.R.S. Received November 30, — Read December 16, 1897. 



(Abstract.) 



These experiments were undertaken with a view to determining- 

 the effect of temperature on thermal conductivities, aud the relation 

 between the conductivity of a mixture and the conductivities of its 

 constituents. The apparatus consisted of a number of flat circular 

 copper discs, into each of which a thermo-junction was soldered. 

 The substances to be experimented on were placed between these 

 discs, heat was supplied to one of the discs at a measured rate, by 

 passing an electric current through a coil in contact with it, and 

 the differences of temperature between the discs were measured by 

 balancing the thermo-electromotive forces produced, against the fall 

 of potential down a wire. About thirty solids, liquids, substances 

 near their melting points, and mixtures of liquids, were tested 

 between temperatures of 15° and 50° C, and the following state- 

 ments embody the results : — 



1. Solids not very good conductors of heat in general decrease in 



conductivity with increase of temperature in the neighbour- 

 hood of 40° C. Glass is an exception to this rule. 



2. Liquids follow the same law in the neighbourhood of 30° C. 



3. The conductivity of a substance does not invariably change 



abruptly at the melting point. 



4. The thermal conductivity of a mixture lies between the con- 



ductivities of its constituents, but is not a linear function of 

 its composition. 



5. Mixtures of liquids decrease in conductivity with increase of 



temperature in the neighbourhood of 30° C, at about the same 

 rate as their constituents. 



