310 Shower of Snails. 
One cannot help suspecting, that the blue precipitates in these 
experiments are occasioned by iro, and yet it is difficult to con- 
ceive how that metal, if present, should escape the observation 
of Dr. Brugnatelli. Further experiments are required, and of a 
more decisive nature, to clear up this matter. 
PRIZE QUESTIONS, 
The Society of Apothecaries of Paris have offered a prize of 
600 franes for—1. The best determination in what manner char- 
coal acts in discoloration, and what are the changes it undergoes 
during the action.—2. What is the influence exercised during 
the operation by any foreign substances which the charcoal may 
contain.—And, 3. To establish whether the texture of animal 
charcoal is not one of the essential causes of its more marked 
action on colouring substances. <A prize of 300 francs will also 
be given for the best vegetable analysis, such analysis to be made 
on a substance used in medicine, or in the arts. The time is 
limited to April ], 1822. 
CONTAMINATION OF SALT FOR MANUFACTORIES. 
The following question having been proposed to the Academy 
of Sciences by the French Ministry: “* What are the processes to 
be adopted in contaminating common salt without injury to the’ 
soda manufactories, which will not permit of its re-appropriation 
to the uses of common life by any secret process, or at so little ex- 
pense as to make the chances or the profits encourage fraud ?” 
The Academy in answering say, That it is impossible to resolve 
the question because of the high price of salt, but that the fol- 
lowing means will render the fraud the most difficult. 
1. Colour the salt by .4, of wood charcoal. 
2. Infect it by z'55 of oil distilled from animal substances, 
or by +45 of tar. 
3. To make the mixture in the magazines. 
SHOWER OF SNAILS. 
A Bristol Paper savs— The inhabitants of this city have 
lately been amused with the exhibition and sale in our streets of 
a collection of snail-shells, which are reported to have fallen, or 
we should more accurately say, made theiy sudden appearance in 
a field of about three acres, belonging toa farmer at Tockington. 
‘An Observer of Nature’ has obligingly directed our attention 
to the natural history of this snail in Montagu’s Testacea Bri- 
tannica. Its name is Limasz vitguta, or Zoned Snail Shell, 
‘It 
