GLEANINGS IN SCIENCE. 
II 
cobwebs will not be obtained*. This solution must be kept about the person till a 
good deal of the turpentine has evaporated, to aid which process it will be advisa- 
ble to have the phial merely closed by a piece of paper tied over it : the older it is 
the better. If any heat is employed to effect the solution, exceeding that of the 
human body, the consequence will be, that the caoutchouc will undergo a change, 
and will never dry or return to its original state. When the India rubber in the 
phial has assumed a viscid consistence, like that of bird-lime, it is in a fit state for 
making cobwebs : the precise condition in which it is most lit for that purpose may 
be known by experiment, and by its sticking two other pieces of India rubber to- 
gether in such a manner, that they cannot be separated when the interposed ce- 
ment is dry. 
The making of the cobwebs is the most simple affair imaginable ; all that is ne- 
cessary is to take a small quantity of the solution on the point of a bit of wood, 
and to stick it to a frame, producing the viscid thread, which will proceed from it 
to the opposite side : in this way any quantity may be made. This process should 
he carried on in a very warm room, otherwise the liquid thread is apt to snap. 
The fibres thus prepared should lie carefully preserved from dust for a day or 
two, till completely dry ; they may then be examined by a microscope, and the 
most even and parallel selected. In this way wfe obtain artificial cobwebs, having 
the same opacity, and the same power of enduring the solar spectrum as common 
ones, and which appear to me to bear as much rough usage, damp, &c. as can rea- 
sonably be desired in such delicate fibres ; for when the turpentine has evaporated, 
they are left neither more nor less titan unchanged caoutchouc. 
IV — MISCELLANEOUS NOTICES. 
[From the Quarterly Journal of Science and Arts, Vol. I. and IT. X. .9 ] 
1. Peculiar Formation of Nitre — The leaves and stems of beet-root contain 
oxalate and malate of potash. Some leaves were tied together, and hung up in a 
warm and slightly-humid place, where there was hut little light, to dry. Being 
examined at the eml of several months, they were found penetrated' with and 
covered by, an immense number of minute crystals of nitre. The oxalic and 
malic acids had been replaced by nitric acid ; but whether from animalized matter 
naturally in the leaves of the plant, or from the action of the air, or in what 
manner, is not known — M Henri Hi; aconnot, Ann. de Chimie, xxxv. 260. 
2. On the Existence of Crystals of Oxalate of Lime in Plants M. Raspail has 
read a memoir to the Academy of Sciences, to prove the analogy which exists in 
arrangement between the crystals of silica, which are found in sponges, and those 
of oxalate of lime, occurring in the tissue of phanerogamous plants. 
The latter crystals were observed, for the first time, by Rafan and Jurine, who 
regarded them as organs of which they knew not the use. They were then observ- 
ed by M. de Candolle, who called them r aphides, and gave a figure of them 
which, however, is inaccurate. These crystals are really very regular tetraedrons’ 
In many plants, as orchis, pandanus, ornithogalunh,jacinthus,phylolaca decandria 
mesemhryanthemum del, aides Kc. they are very small, not being more than of 
a millimetre (.0002 of an inch) m width, and ,' 5 (.004 of an inch) in length. But, 
,, ‘. T , , ' e , re always be the same difficulty in obtaining traly parallel and even 
threads from the Caoutchouc as there is from conunou cobwebs. Lliave one of Messrs 
trouguton and turns s best micrometers by me at this mmncnl : and the cobwebs' 
thongb I of course picked, and abundantly even enough for practical purposes, are oer- 
tainly for Irom being of the same diameter throughout. I suspect, from microscopical 
examination, that a common cobweb is a flat thread like a piece of tape, not a round one • 
so that, it it is at all twisted, it must present different apparent diameters to the eve’ 
r he best way of getting parallel threads with the India rubber paste, appears to nJtn 
e. to let it stand lot a considerable time without anv agitation or stirring up v halever 
and when the instrument is inserted to draw out a thread, to disturb ll, ", r ( 
as possible, icmd, mg „„| v iis surface ; the more the thread is drawn out themore even 
nd true it becomes, ] t may not he irrelevant to mention, that in order to give the fibres 
ihw'"" St i degl ?° ®f slK "ffth, they should be put on in the lowest decree of tension 
possible . in drawing them 0 „ t on t| ]t . frame, therefore. Jet the instrammt . - i 
as it will before the end of the thread is fastened down, that at least the canntehnn " C 
not be stretched till its ultimate attachment to the mic’remeter is mim l.eA u ; 
white naphtha may be tried instead of the turpentine. 1 ’ d ‘ Iu;oU leit 
