./. W. Shipley — Volcanic Emanations in Alaska. 143 



edly present in the lower part of the valley ten miles 

 below Novarupta, The surface of the mud flow was 

 impregnated with HC1 condensing from the vapors pass- 

 ing over it. The presence of HF was not suspected until 

 large deposits of amorphous Si0 2 were observed around 

 vents from which issued strongly acid vapors. Laterits 

 presence was indicated by the etching of the gas-washing 

 bottle into which the vapors were pumped and condensed 

 and in the laboratory where fluorine was found in the 

 majority of the incrustants examined. 



Hydrogen sulphide and sulphur dioxide were common 

 constituents of the evolved gases. In one instance, from 

 a vent depositing flowers of sulphur S0 2 was strongly in 

 evidence, while the lead acetate paper indicated the pres- 

 ence of sulphide, Possibly the gaseous reaction between 

 the two gases was not complete or else a volatile sulphide 

 other than H 2 S was being emitted. 



Volatile ammonium compounds were detected in almost 

 all of the vapors examined. Some were very strongly 

 impregnated and as already mentioned NH 4 C1 was crys- 

 tallizing in the throat of vents on the western rim of 

 Novarupta. These were relatively cool, acid fumaroles 

 from which the gases were issuing under low pressure. 

 The salt collected in an annular mass on the walls of the 

 vents a couple of feet within the orifices. Below the 

 accumulation, the salt was no doubt dissociated into its 

 gaseous constituents NH 3 and HC1. A 4-oz. bottle filled 

 from one of these vents analyzed 98% NH 4 C1. 



A rather interesting relationship between the growth 

 of blue-green algae and the presence of ammonium com- 

 pounds in the emanations was established. Algse were 

 found growing up to the edge of vents where the thermom- 

 eter indicated 100 °C. No algse grew where the vapors 

 showed an absence of ammonium. This relationship held 

 over the large areas where the gases were slowly exud- 

 ing through the porous mud flow. Apparently, the evo- 

 lution of ammonia compounds was quite general, for the 

 afternoon sun disclosed the slopes surrounding Nova- 

 rupta clothed in a coat of green provided by the growth 

 of algae. 



Sulphur. — Sulphur deposits were not met with so fre- 

 quently as might have been expected from the chemical 

 conditions obtaining in the vapors. From the hotter 

 vents the sulphur would escape into the atmosphere, but 

 the most of the sulphur was fixed as sulphide, sulphates 



