89 
in any way from those which I have shewn occur in Sigil- 
laria vascularis ( Quarterly Journal of the Geological Society 
for May, 1862, Plate 1, fig. 6). . Indeed, the transverse 
section of the specimen there figured would almost do for a 
representation of Stigmaria , if the latter had the central axis 
preserved, which it unfortunately has not. There is the 
same internal radiating cylinder and the same space formerly 
occupied by lax cellular tissue, which gradually passes into 
the elongated tubes or utricles arranged in radiating series, 
and parted by large bundles of vessels next to the bark ; thus 
clearly proving from structure alone that Stigmaria is the 
root of Sigillaria , each of them having an inner radiating 
cylinder composed of barred vessels, a space occupied by lax 
cellular tissue, and an outer radiating cylinder composed of 
elongated tubes or utricles. 
Mr. Binney also exhibited some of the specimens to the 
meeting, and said that he was in possession of clear evidence 
both from structure and branching to prove that Sigillaria , 
which was the chief plant from which our beds of coal had 
been formed, was a tree which branched like the Lepidoden- 
dron , and was not the strange stunted-topped plant which 
some authors had represented it to be. 
The President drew attention to the late fatal explosion 
at Peterborough, and asked whether the easy method of 
testing steam boilers, described some years ago by Dr. Joule, 
was forgotten or found to be impracticable? 
Dr. Joule said that he had taken pains to give his method, 
by which the testing by hydraulic pressure could be applied 
with the utmost facility by simply filling the boiler with 
water and then raising its temperature a few degrees, a very 
extended publication. He believed that the objection raised 
by some to its use, was the absurd one that hydraulic pressure 
injured the boiler. The very object of a test was to detect 
weak boilers for the purpose of strengthening or rejecting 
