GREGORIAN a.
scope, named from Prof. James Gregory, of Edinburgh, who perfected it in 1663. A small concave mirror in the axis of this telescope, having its focus coincident with that of the large reflector, transmits the light received from the latter back through a hole in its center to the eyepiece placed behind it. -- Gregoria…
ICHTHYOSAURUS n.
An extinct genus of marine reptiles; -- so named from their short, biconcave vertebræ, resembling those of fishes. Several species, varying in length from ten to thirty feet, are known from the Liassic, Oölitic, and Cretaceous formations.