March, 1919] Temperatures of Ten Thousand Smokes 253 



equipment, to proceed to examine all vents in the area selected 

 for study. It was our custom to proceed rapidly, giving the 

 vents a preliminary examination with a thermometer which 

 read to 210° C. It could be thus readily determined whether a 

 given vent was merely at the boiling point — which of course is 

 the temperature of the vast majority of the orifices— or whether 

 it was higher. 



When this preliminary examination showed a temperature 

 above 100° C, and the fumarole v/as so situated that it was 

 accessible for measurement by our instruments, the packs were 

 opened, a record of the temperature secured by the pyrometers, 

 and the position of the vent recorded by means of magnetic 

 readings on a Brunton compass, from fixed triangulation 

 stations on the mountains around the Valley. 



But many of the largest and most important volcanoes of the 

 Valley were so situated as to make it altogether impracticable 

 to measure their temperatures with our instruments. Thus, 

 although Novarupta has every appearance of being the climax 

 of the activity of the Valley, we were unable to reach any vent 

 in its vicinity whose gases were more than 100° C. 



In order to judge rightly the degree to which the results 

 obtained may truly represent the activity of the Valley, the 

 reader should, therefore, understand some of the limitations of 

 the instruments with which they were secured. 



In the first place, our thermocouples were insulated with 

 unglazed porcelain tubes for about two feet at the end, and 

 above that with asbestos. Now, if the wires touched or 

 were short circuited at any place other than the twisted couple, 

 the temperature recorded would be that of the junction 

 nearest to the registering instrument. Therefore, the asbestos 

 insulation which protected the wire was all right as long as the 

 instruments wete dry, but if the steam condensed and saturated 

 this covering or the two wires touched, the resulting temperature 

 would be that of the condensed steam, or about 100° C. This 

 occurred frequently because the steam would condense where 

 it came in contact with the cold air at the side of the hole. 

 We overcame this by bending the wires so that they did not 

 touch each other while in the steam. As almost every fumarole 

 necessitated a different bending of the wires, the asbestos 

 insulation and porcelain tubes were subjected to considerable 

 wear and tear. 



