D. P. Todd—Search for a Trans-neptunian Planet. 225 
upper beds alone extend with a thickness of from10 to 30 feet. 
The purple sandstones deposited in the hollows of the Silurian 
limestone are characterized by the presence of Placoganoid 
fishes of a Devonian type. The Silurian limestone was exten- 
sively eroded antecedent to the deposition of the superjacent 
Devonian beds. Hollows 80 feet deep are seen that were worn 
in the evenly bedded strata. The upper 235 feet may belong 
to about the time of the Carboniferous group. The 450 feet 
of mottled limestone and 100 feet of arenaceous, micaceous 
shales is shown to be of Primordial age by the presence of Lin- 
gulepis prima, Conocephalites and Bathyurus in the upper portion, 
and Hyohthes primordialis, Lingulepis, Crepicepalus, and the 
species found above in the ‘lower beds. 
he missing Silurian groups may not have been deposited 
in this region, or, what is quite probable, their representatives 
were removed in the period of erosion that followed the close 
of the Silurian time, and has left traces of its action in the hol- 
lows oe irregular surface over which the Devonian beds were 
sprea 
ArT. XXVITL.— Preliminary Account of a Shiocaiihiioe and 
Practical Search for a Trans- se rami Snes y Dek, 
Topp, M.A., Assistant Nautical Almana 
Introductory and Historical. 
THE suggested probability, on scientific sartteae e oes there 
revolves about the sun a second planet exterior to t it of 
ranus, is not new. So early as 1834, when the doemven 
astronomers of the day were by no means settled in their con- 
victions that even the ‘greater portion of the then rapidly in- 
creasing residuals in the longitude of Uranus was due to the 
perturbing action of a single exterior planet, Hansen is credited 
with expression of the opinion, in correspondence with the 
elder Bouvard, that a single planet would not account for the 
differences between theory and observation.* Dr. Gould, how- 
ever, in his Report on the History of the Discovery of Neptune,+ 
says, “I have the authority of that eminent astronomer himself 
[Hansen] for stating, that the assertion must have been founded 
expressed or entertained that belief.” Professor Peirce’s criti- 
cism of the ‘investigations of LeVerrier, to the effect that his 
predicted orbit of Neptune was so widely discordant from its 
* Memoirs Royal Astronomical Society, vol. xvi, p. 388. 
Published by the Smithsonian Institution, 1850, 
Am. Jour, Sct. oo eee Vou. XX, No. 117.—Sxpr., 1880, 
