88 Improvements in Physical Science (JAN. 
But if the fresh water is very gradually impregnated with salt, they 
can be made to live in it when of the strength of sea water without 
any injury. When the same experiments were tried with sea water 
molusca, the result was the same. If suddenly plunged into fresh 
water, they died. But if the sea water was slowly reduced by mix- 
ing it with a greater and greater proportion of fresh water, they 
may be gradually accustomed to live in fresh water, Water im- 
pregnated with sulphate of lime, or with carbonic acid, or saturated 
with common salt, very speedily destroyed all the molusca put into 
it. Hence M. Beudant thinks we can explain why no shells are 
found in gypsum or rock salt. Ann. de Chim. et Phys. ii. 32. 
3. Mr. Dicke’s curious account of the destruction of the gaste- 
rosteus aculeatus, or three spined stickle-Lack, by the tenia solida’of 
Gmelin (see Annals, vii. 106) affords ample subject for physiological 
speculation. 
4. Dr. Balfour’s important experiments on the re-union of parts 
of the human body accidentally separated, are sufficiently known to 
my readers, as [ inserted an historical account of the whole in the 
Annals, vii. 263. 
5. It would be dificult to give a satisfactory explanation of the 
fish which make their appearance in tanks in India after rain, as I 
have stated in the Annals, viii. 70. 
6. In the first number of the Journal of the Royal Institution, p. 
55, Mr. Ireland has given a distinct account of the changes of the 
Surinam frog, from the tadpole or fish state to that of the frog. 
These changes were not before understood, and have occasioned a 
good deal of discussion among naturalists. 
7- Inthe same Journal, i. 86, Sir Everard Home relates the case 
of a gentleman, aged 53, who in consequence of a paralytic stroke 
from which he recovered, lost the power of adjusting his eye to near 
distances. He could observe a pin upon the carpet at the distance 
of ten feet, but was unable to read the newspaper. 
8. Sir Everard Home relates in the same journal a curious expe- 
riment of Mr. John Hunter, confirming an opinion universally 
credited by all ass keepers, namely, that an ass will not continue to 
give milk after she has lost the impression of her foal. He took an 
ass in milk that had a foal, and kept them apart every night, but had 
the mother milked in the morning in the presence of the foal. 
This was done for more than a month without there being any 
diminution in the morning’s milk. The foal was taken away alto- 
gether, andthe mother was milked instead of being sucked by the 
fcal, particularly in the evening at the same hour at which the foal had 
been taken away from her, and again in the morning at the usual 
hour. The milk taken in the morning was always compared with 
that taken the morning before. But in three mornings the quan- 
tity was lessened, and the fifth morning there was hardly any; the 
foal was then restored to her, but she would not allow it to suck. 
The experiment was repeated with a similar result. 
9. In the same Journal, i. 297, a case is related by Mr. Everard 
Brande, of a lady who swallowed from one to two tea-spoonfuls 
of magnesia every night for two years, and was in consequence 
