484 Scientific Proceedings, Royal Dublin Society. 
nor would it be difficult to cause the crucible to regulate its 
own temperature by the changes of resistance which a platinum 
thermometer placed within the heated muffle would experience. 
It is apparent that for experimental petrology this method of 
utilizing electric energy in maintaining constant temperatures for 
long periods and local in application should prove of value. 
Where platinum wire is not used, the life of the crucible is. 
briefer, owing to the largely unequal expansion of the wire and 
the fire-clay. This difficulty might be obviated by imbedding the 
wire, in the first instance, not naked, but covered by a substance 
which, on the baking of the crucible, would be removed; e.g. a 
non-conducting fusible material {as paraffin wax), or a cotton 
covering which would be practically removed by combustion. In 
this way space would be left in which the wire might expand. 
The particular manner in which the wire is coiled is not of 
importance, provided it is distributed with approximate uniformity 
throughout the fire-clay; a flat spiral for the bottom, rising in an 
expanding helix in the walls, isthe form I have found most useful. 
For some purposes it may be advisable not to imbed the wire, but 
to insert it between an inner and an outer refractory vessel. 
