SCIENTIFIC SUMMARY. 
443 
mersed in the liquor^ the metals copper^ cadmium, and thallium, jointly. 
The metallic spongy mixture thus obtained is rapidly washed — first with 
water, by being placed in a bag made of woollen fabric ; next, some sul- 
phuric acid is added to the wash-water, whereby the metals thallium and 
cadmium get dissolved with evolution of hydrogen, while copper is left un- 
touched ; from the acid solution so obtained thallium is precipitated, by 
means of iodide of potassium, as a pure yellow iodide, which is further 
purified by washing and by decantation ; from the remaining liquor cadmium 
is precipitated in the metallic state by zinc. One cubic metre of the above 
liquid yields in a few days 6-4 kilos* of spongy metallic precipitate, contain- 
ing 4-2 kilos, cadmium, 1-6 kilo, copper, and 0-6 kilo, thallium, 7'4 kilos, of 
metallic zinc becoming dissolved. The solution of cadmium and thallium in 
sulphuric acid yields, on addition of 0-5 kilo, iodide of potassium, 0’97 kilos, 
of iodide of thallium. Thallium may be precipitated from the sulphuric 
acid solution by means of chlorides, but in so doing a not inconsiderable 
quantity of the metal is retained by the cadmium. The thallium may be 
directly obtained from the first liquor at once by precipitation with iodide 
of potassium, provided previously a sufficient quantity of hyposulphite of 
soda be added to keep the copper in solution ; the application, however, of 
this latter method interferes with the object for which the liquor is pre- 
pared, viz., the making of sulphate of zinc. — Polyt. Centralhl., 1868, No. 10. 
Diamonds in Cape Colony . — At the British Association meeting, Professor 
Tennant made a communication on the recent discovery of diamonds in 
Cape Colony. This gem, he stated, had been found somewhat abundantly 
recently in the above district \ and he exhibited the casts of some weighing 
9 carats, worth 500/. Some agate, chalcedony, and other precious stones 
found in the same deposit had been sent him, but he would have preferred 
some of the sand and mud in which they were deposited. One diamond 
found very recently weighed as much as 15^ carats. He was of opinion that 
before long we should have a large collection of diamonds from the above 
country, adding that, although we had heard a great deal of diamonds being 
found in Australia, those stones were not worth now so many pence as 
pounds had been asked for them. 
METEOEOLOGY. 
The Nature and Phenomena of Hail. — M. the Abbe Lecompte has been 
good enough to send us a copy of his very valuable memoir on hail, which 
has just been published in the Proceedings of the Royal Society of Belgium. 
All who care for this department of meteorology should possess the 
memoir. We shall, however, give a few of M. Lecompte’s conclusions, 
which are generally expressed in a vast number of tabular schemes and 
curve-diagrams. Erom a series of observations extending over three years 
he concludes that the greatest quantity of hail falls* in March and April, 
and also that more falls between three and four in the afternoon than 
during any other two hours in the twenty-four. As to the form of the hail- 
stone he says he has observed that the stones are most usually small globular 
H H 2 
