ABSTRACT OF PROCEEDINGS. XXX1. 
ness evidently being due to a normal thinning in that direction. 
This in the writer’s opinion paves the way for a complete thinning 
out of the upper portion of the measures under Sydney. This 
possibility is again evidenced in the Mount Westmacott and Holt- 
Sutherland No. 3 Bores, in-which No. 1 seam was proved to have 
diminished from 12 feet at Helensburgh to 4 ft. 84 in. and 4 ft. 
2 in. respectively. With regard to the southern extension of the 
Northern Coal Field, it may be again pointed out that no seams 
comparable in thickness with Nos. 1, 2 and 3 were proved by the 
Hawkesbury River Bore, so that a thinning from that end towards 
Sydney has been proved. ; 
The second point brought forward is the pronounced split proved 
in the opening up of the Sydney Harbour Collieries coal seam. 
One of the features of the Bulli seam is that no split has ever yet 
been found in it where its identity is undoubted. Having regard 
to the origin of splits, it seems unlikely that one would occur in 
the central portion of the area of deposition and not in the peri- 
pheral portion. 
A third item for consideration, and one more tangible than 
either of those already advanced, is the finding of Glossopteris 
impressions at least 4 feet 74 in. above the roof of the seam in the 
Balmain shaft. Great importance is placed upon this fossil in 
determining the upward limits of the Permo-Carboniferous forma- 
tions in New South Wales, and Professor Davin has laid particular 
stress upon the fact that there is not a single instance on record 
of Glossopteris having been found above the top seam of the 
Northern coal field. Mr. J. E. Carne, Assistant Government 
Geologist, had the same experience in the Western coal field, and 
was unable to record the presence of Glossopteris above the 
Katoomba seam, which he correlates with the Bulli seam. 
During the geological survey of the Southern Coal Field par- 
ticular attention was paid to this important question, but no 
specimen of Glossopteris was found overlying the Bulli seam. 
This evidence all serves to confirm the opinion held by our leading 
