552 
CONVERSAZIONE. 
other curiosities, as remarkable for beauty as for scientific interest. Thallium, 
the element discovered by Mr. Crookes, F.B.S., by means of spectrum ana¬ 
lysis, is now distinctly recognized as a metal holding a kind of intermediate 
position between potassium and lead. Thus, the element itself resembles lead 
in appearance, and it may be preserved under water, but the oxide, T1 2 0, like 
K 2 0, is soluble in water, giving a caustic alkaline solution. The chloride, like 
that of lead, is only sparingly soluble in water, crystallizing from a hot solu¬ 
tion in small prismatic crystals ; whilst the sulphate is soluble in water, and, 
with sulphate of aluminium, furnishes an alum which is deposited in octakedra. 
There are other compounds, such as the acid tartrate and the emetic tartar, 
etc., which illustrate the same points. All these were represented by speci¬ 
mens of perfect purity, and weighing each several ounces. In the same case 
were to be seen also specimens of boron and silicon, zirconium, and other bo¬ 
dies rarely obtained in the elementary condition. 
Messrs. Hopkin and Williams have very handsomely presented to the 
Museum two large specimens, one of ammonia alum, the other chrome alum, 
beautifully crystallized. 
An unusually large sample of meconine, the produce of several hundred¬ 
weights of opium, and a well-crystallized specimen of platino-cyanide of mag¬ 
nesium, a compound which exhibits dichroism most beautifully, were contri¬ 
buted by T. IN. It. Morson, Esq. 
Living specimens of Hippocampus and Pipe-fish were shown in the La¬ 
boratory by Mr. C. H. King. These very singular little fishes were brought 
by Mr. King from the Mediterranean, and as living specimens must be looked 
upon as great curiosities. The Hippocampus , or Sea Horse, is so called from 
the resemblance the head presents to that of ahorse when bent at about right 
angles to the body. They possess no tail-fin, but support themselves in an 
erect position by the tapering extremity, which they twist round the stems 
of sea-plants. The most singular part of their character, however, is the 
solicitude they exhibit in the care of their young. In this duty it appears, 
the male, unlike those of the higher animals, takes the principal share, pro¬ 
tecting the young fry in a pouch of peculiar construction, provided near the 
base of the tail. Mr. King also exhibited specimens of the Bombyx cynthia, 
the new Silk-worm and Moth. 
Hot the least interesting of the numerous exhibits was the remains of a 
Dodo, recently brought from the Mauritius by M. H. Baissac, pharmaceutical 
student. The remains- consisted of bones of both legs, a portion of the ster¬ 
num, the pelvis, and several of the cervical vertebrae. When the island of 
Mauritius was discovered, about 350 years ago, the Dodo was still existing 
there in abundance, but in the course of a few years it was completely extir¬ 
pated. All that now remains of this bird, which from the accounts handed 
down to us was larger than a swan, are a few bones, one collection of which 
is to be found in the British Museum. 
There was a large displa} 7 ' of microscopes of every description, contributed 
by Messrs. Boss. Murray and Heath, Ladd, Horne and Thornthwaite, H. 
Baker, J. How, B. and J. Beck, The London Stereoscopic Company, Collins, 
and Waddington. Ingenuity and skill in the preparation of new objects for 
the microscope seem to have been expended chiefly in the production of crys¬ 
tals. Mr. Martin, of the London Stereoscopic Company, showed some ex¬ 
ceedingly beautiful specimens of “ spiral sulphate of copper.” This salt, 
when permitted to crystallize from warm solutions, assumes, according to the 
temperature, a spiral appearance, as though the solution during the process 
had been full of minute whirlpools. In this condition it constitutes a most 
attractive object for the polariscope ; the small plates of which the crystals 
seem to be made up including, no doubt, between them films of air, and so 
giving rise to phenomena of “ interference.” 
