304 Miscellaneous. 
obtained from a great variety of plants, if the natives could be prevailed upon to 
use the precautions requisite for procuring a superior article. The South Ameri- 
can caoutchouc was much superior in value from this circumstance alone, since 
that from the east was of equally excellent quality. At present, that from Para 
sells at 2s. 6d. or 3s. per pound, whilst the East Indian fetches only 2d., and 
can be used merely for the purposes of distillation, in manufacturing the caout- 
choucine. The material was now obtained, or could be obtained from many 
countries of the east, and by further research it would most likely be found to 
exist in several other species than those in the same families from which it was 
now procured. These families were stated to be Cichoraceae, Lobeliaceae, 
Apocyneae, Asclepiadeae, Euphorbiaceae, Artocarpeae. Professor Royle had re- 
marked that bird-lime was often made from plants producing caoutchouc, and 
that these had their woody fibre particularly strong and tenacious. Coupling 
this fact with the circumstance of the silkworm feeding on the same or similar 
plants, he feels inclined to believe that caoutchouc may form an essential ingre- 
dient in their food. He had procured an analysis to be made of the juices of the 
mulberry, and found them to contain caoutchouc. 
Mr P. Duncan proposed a query, which was not fully answered, whether the 
animalcules which produce the luminosity of the sea, ever emit their light under 
water, or without first coming to the surface ? 
Dr Hancock read a paper on a species of cow-fish closely allied to the Mana- 
tus fluviatilis, but which he considered to be distinct. He had noticed it in the 
interior of Guiana, but it is now rarely to be met with any where near the Euro- 
pean colonists. The species grows nearly to the length of nine feet, and weighs 
about 800 lb. He thought this animal might be easily domesticated. Dr Riley 
thought it doubtful whether the animal described by Dr Hancock might not be 
a dugong ; and noticed an error in Cuvier, who asserted the Manatus Americanus 
to have only thirty -two teeth, whereas he now exhibited a skull of this species 
in which thirty-six might be observed, or rather the places which they occupied ; 
for it always happened that the anterior molars were shed when the posterior 
were being protruded. The places of two incisors were certainly to be found 
in the upper jaw, and probably there had also been two in the lower. 
Dr Macartney explained his method of preserving animal and vegetable sub- 
stances from the attacks of insects and other sources of decay. For this pur- 
pose he used a concentrated solution of equal parts of alum, nitre, and salt, mixed 
with an equal proportion of proof spirits of wine, to which a little essential oil, 
either rosemary or lavender, had been added. He recommended also the use of 
pyroligneous acid, and then a coat of plaster of Paris, which might afterwards be 
removed when the object was thoroughly dry. 
A collection of beautifully preserved specimens of North American insects, 
procured by some persons in Bristol, was exhibited by Mr Hope. These insects 
were imported in casks of raw turpentine, and when this was dissolved, they 
floated to the surface, whence they were taken, and after being immersed in spi- 
rits of turpentine, to remove the turpentine with which they were encrusted, they 
were set out in the way which is usually pursued by entomologists. 
Thursday, <25th August Dr Richardson's Report concluded. 
A communication from Dr Moore, stated that he had taken the Triyla cata- 
phractes in Plymouth harbour, and which was the first time this fish had occur- 
