A CONTRIBUTION TO THE STUDY OF AUSTRALITES. 
29 
3rd. That this antitrade did not pass the Polar limit of 
the trades, but deviated more to the right in the 
Northern Hemisphere, and to the left in the South- 
ern, so as to become a current from the west over 
the crest of the barometric maximum of the tropics, 
where it descends to increase the trades. 
Mr. Cooke informed me that the barometric maximum in 
Australia varies from about latitude 25' S. in winter to 35 S. 
in summer. 
This, as I understand it, means that the upper cirrus clouds 
at the equator travel constantly from east to west, tending to 
diverge north or south, as the case might be, and at from 25 
to 35° north or south turn towords the east, becoming south-west 
wincls to the north and north-west winds to the south of the 
equator respectively, with a tendency to turn more towards 
the east in both cases. 
Now, if this be true, and the statement regarding the velocity 
of this air current, which I have seen elsewhere affirmed to be 
from 60 to 80 miles per hour, be also true, it would quite account 
for the distribution of Australites and Billitonites, if they were 
derived from one or more of the numerous unexplored volcanoes 
of the East India Islands. 
It would account for these bodies being restricted in their 
distribution to the small portions of the globe where they are 
found. It would account for their formation being spread over 
such a long period of time, as I think I have proved is certainly 
the case, from the late tertiaries even probably up to the present. 
It would explain why Australites are more numerous than Billi- 
tonites, as these volcanoes, mostly lying to the south of the 
Equator, more would naturally come south than would go north. 
It would also account for so few being found within the 
tropic generally, as the perfect bubbles would not tend to drop 
so soon and the deformed ones would have dropped earlier, 
though the scarcity of population and the heavy rains may have 
something to do with it. 
It is curious that the button form occurring with reasonable 
frequency in the Eastern States is not found in Western Australia 
as far as I know, and the tabloid form, which is one of the common- 
est here, is not figured in any plates that I have seen as occurring 
in the East to my recollection. (Compare bigs. 1 to 3 with bigs. 
4 to 9, in Plate XXI.) 
This would point probably to more than one source for their 
formation, or it may be that the Eastern form, which it is sug- 
gested by Mr. Dunn is represented with us by the conical one, 
has been the bleb of a more perfect or less fragile bubble. 
As 1 will explain later, there are reasons why I cannot agree 
with Mr. Dunn that our conical form is derived from a form 
