SCIENTIFIC SUMMARY. 
327 
nection with the order of plants to which the species now founded belongs. 
The fossil belonged to an arborescent cycad resembling in aspect the tall 
cylindrical stems of Cycas or Macrozama, and differed in this respect from the 
spherical or ovoid trunks belonging to the genus, which were described by 
Buckland and Lindley. The cellular axis was relatively very large. The 
pith has disappeared, except in one of the specimens, where there are still 
some indications of it, and of the vascular bundles which abounded in it. 
The woody cylinder surrounding the pith consists of two rings, everywhere 
pierced by medullary rays, which are often so large as to separate the rings 
into numerous series of woody wedges, as in recent Cycadece. The presence 
of discs on the woody vessels has been detected both by Professor Morris and 
Mr. Carruthers. The inner surface of the woody cylinder is marked by 
numerous narrow grooves and perforations, formed by the vascular bundles, 
as they passed from the pith into the wood. The outer surface has similar 
scars, produced by the vascular bundles, which passed from the wood to the 
leaves j but they are here larger and more regularly disposed than on the 
inner surface. Between the wood and the bases of the petioles there inter- 
posed a very thin layer of cellular tissue, through which the vascular bundles 
passed in an upward direction towards the petioles. 
MECHANICAL SCIENCE. 
Institute of Naval Architects . — During the month of April this Institute 
held its annual meeting, and, as in preceding years, some of the papers were 
of the highest scientific interest. Mr. I. B,. Napier read a paper on some 
steel tug- boats constructed for the Godaverv, having the extraordinary propor- 
tions of 140 ft. length, 25 ft. breadth, and only 1 foot draught. The plating is 
of galvanised steel with a view of reducing to the utmost the weight and 
frictional resistance and securing durability. An awning or roof, also plated 
with steel is provided, forming an integral part of the structure, being con- 
nected with the bottom by lattice-frames, so as to increase the depth, resisting 
bending strains, and thus to render the vessel rigid. The engine has a pan 
of 11-inch cylinders, 4-ft. stroke, supplied with steam at 150 lbs. pressure, 
from a tubular boiler, of the locomotive type. The paddles are at the stern, 
and the propelling surface is not less than of the augmented surface. It 
is thought that the speed may reach 12 miles an hour. 
In a paper on the Stowage of Merchant Vessels by Mr. Barnaby, a 
practical plan was suggested for ascertaining the crankness or stiffness of 
the vessel, due to loading. Mr. Barnaby suggests the securing the ship to 
the wharf-side, by a chain with a slip, when she is lifting with the tide. 
Having thus been heeled over a few degrees she is to be suddenly released 
and the oscillations in a given time counted. In some experiments on the 
u Madeline ” yatch, the shifting of a weight of 86 cwt. on the mast caused 
the time of 5 oscillations to vary from 21 to 26 seconds. 
Mr. Bourne described a system of designing the water lines of ships, soi 
that the lateral displacement of the water for a given progress of the vessel 
should obey the same law as to velocity as a pendulum. 
