94 
paper by this gentleman on the height of 
the aurora borealis above the surface of the 
earth, which appears in the last part of the 
Philosophical Transactions, we extract the 
following results, viz. that the luminous 
arches of the aurora which occasionally ap- 
pear stretching from east to west, are all of 
the same height, and that height about one 
hundred miles. What length the upright 
beams, or, to speak more properly, ‘those 
parallel to the dipping needle, may be, 
which are the ordinary forms of the aurora, 
we have not observations to determine. 
Whether those beams arise above the arches 
as from a base, or whether they descend be- 
low, as if appended to the arches, we cannot 
absolutely determine. If the parallel bands 
be usually about twenty degrees asunder, 
their distance from each other will be about 
thirty-six miles. It is remarkable that the 
arches and beams should rarely, if ever, be 
seen cognate or in juxta position, but al- 
ways in parts of the heayens at a consider- 
able distance from each other. 
Rowing by Steam.—The employment of 
steam vessels for the purpose of tracking on 
canals, has hitherto been found impossible, 
the wave created by the action of the paddles 
being such as would entirely destroy the 
banks, unless they were faced with brick- 
work or masonry. Some attempts to ob- 
viate this by diminishing the velocity of the 
wheels have recently been made on the 
Forth and Clyde canal with tolerable suc- 
cess ; and at the beginning of the month 
of December, some experiments were made 
in the Thames with paddle-wheels con- 
structed according to the plan of Lieutenant 
Skeene, in which the floats, having a motion 
on an axis, offer but little resistance, when 
being raised from the water, when, in addi- 
tion to the speed of the vessel being consi- 
derably increased by this contrivance, it was 
found that the wave thrown off laterally was 
coniparatively so trifling as to afford a rea- 
sonable prospect of steam boats being intro- 
duced on canals, without any mischief result- 
ing to the banks. 
New Fulminating Powder.—A German 
chemist has discovered, that by mixing two 
parts of nitrate of potash, two parts of neutral 
carbonate of potash, one part of sulphur, and 
six of sea salt, all finely pulverised, a fulmi- 
nating powder of the greatest strength is 
obtained ; and what is very remarkable, the 
force of the explosion is constantly directed 
below. 
Fioses.—M. Desportes, an’ experienced 
French botanist, has recently published an 
account, professedly of the roses indigenous 
in France; but as it appears from his preface 
that those of England as well as of France 
are the subject of his labours, we think 
that the following abstract of his researches 
will be interesting to our readers. He di- 
vides into eleven tribes the seventy-nine 
species of the rose, which are actually 
known, omitting eleven doubtful species, to- 
gether with their varicties. The number of 
Varielies. 
[ Jan. 
varieties which may be considered as ascer- 
tained amounts to 2,533, divided very un- 
equally among the species, as may be seen 
in the following table, in which the most 
interesting species are enumerated. 
Species. Varieties, 
Rosier mousseux ........ 18 
des chiens ........ 20 
des Alpes i!nv.t.cas ewan 
———— de Eranefort sence ey 
Bs eGo PEPYS Cen bE 
— rubigineux....... : 57 
= = MOIsette +. eae ee 89 
=) de! dantas ft #5. see 
——— icent feuilles” =e Sen a8 
— pimprenelle ...... 123 
LATA clot iol ol nimi ete ees 
—————. ‘de Bengale’ #27... ga08 
de Provins...-.... 1215 
Electricity.—An interesting discovery, 
made by M. Becquerel, was communicated 
to the Institute of France in November last. 
It is known that when the two poles of a 
voltaic pile are connected by a short wire, 
and a proper charge is passed through it, 
the middle of the wire becomes red hot. 
This phenomengn has generally been ex- 
plained by supposing the temperature of the 
wire to be the same throughout its whole 
extent, but that the extremities being first 
cooled in consequence of their contact with 
the pile, the middle alone should display a 
more elevated temperature. M. Becquerel, 
who has been engaged for a long time in 
investigating the nature of the electric prin- 
ciple, proposed to determine the temperature 
of the different points of a metallic wire, of 
such a length as that the effect of the cool- 
ing of the extremities need not be appre- 
hended, when this wire is traversed by an 
electric current. ‘The result of this experi- 
ment showed that the temperature continues 
to increase from each extremity to the 
middle, and that consequently the cause 
which creates an electric current, of which 
the intensity is constant in each point of the 
wire, acts as an accelerating force for deve- 
loping heat. 
Steam Packets to India.—A Mr. Tho- 
mas Waghorn, of the Pilot Service in the 
Ganges, has proposed to bring out the mails 
to Calcutta from England (making Fal. 
mouth his port of departure) in seventy 
days. The vessel for the intended experi- 
ment is to be of about 280 tons; the masts 
of the vessel are to be after the fashion of 
the row boats of the river, to be made short, 
and to strike at pleasure. She is to have 
very square yards, of the lightest possible 
dimensions, as lightly fitted as can be, and 
to spread by means of studding sail booms, 
&c. a press of sail, the canvass being of the 
lightest qualities which will stand a breeze ; 
masts and yards to be so rigged, that in four 
hours they may be got up or down. The 
vessel will be schooner rigged if on a wind, 
having lower top and top-gallant gaffs, and 
square rigged when before it. In order to 
have the whole space of the vessel under 
