surgeon of a ship at W hydah, during the H arm attan, w ithout a
single individual taking it, although they all sickened o f i t when
th e inoculation was repeated on th e cessation o f this wind. T he
Kamsin is called the “ h o t wind” in E gypt, and in M adeira (where
it is called th e Sirocco by th e B ritish, and L este by the P ortuguese)
it sometimes raises th e therm om eter to 90° in th e shade; b u t
on th e G old Coast, if I recollect right, it lowers th e therm om eter
from 5 to 10 degrees. T he easterly current from Cape Palmas is
always reversed during th e H arm attan, and I have known a vessel
run up from Cape Coast to Sierra L eone in five days, by taking
advantage o f this circumstance ; it generally takes from three
weeks to a m onth to beat u p there. I feel im patient for the
opportunity o f m aking some hygrom etrical observations during
th e H arm attan, and propose to ascertain the positive quantity of
hum idity contained in th e air a t th a t time, by means o f a doubly-
graduated tube and a trough o f mercury, allowing a small quantity
of air to enter at th e tube, after th e m ercury w ithin it has been
gradually raised to ebullition, noticing th e quantity o f air by the
great scale of th e tube, and the height o f th e m ercury by the'lesser,
observing th e barom eter and therm om eter, calculating th e volume
of air contained; afterwards introducing a drop o f w ater to
saturate it, calculating its volume a t th e tem perature o f the
atm osphere, and w ith it, th a t o f th e air perfectly dry, deducting it
from th e volume found in th e first instance, and calculating the
w eight of m oisture contained in th e residue. T his strikes me to
be th e surest m ethod, w hen th e occasion is too interesting to
depend on th e m ere comparative indication of hygrometers.
T h e insufficiency of m y means would have entirely deprived m e
o f instru m e n ts for th e more interesting m agnetic observations'?,
“ La physique y pourra enfin obtenir aussi les lois de la distribution dumagnétisme
terrestre, dont, partout l’intérieur de l’Afrique, on n’a pas la njoinjlrq notion j elle y
trouvera encore des données météorologiques d’un intérêt extrême.—B io T (Review of
the Mission to Ashantee), Journal des Savane, Août.
being the m ost expensive o f any V had not M. Arago kindly
presented me w ith th e simple apparatus which he used at
D u n k irk ; viz., a needle w ith an ivory scale affixed to th e end
of it; covered by a glazed box, to prevent its being agitated by
any current of air, and suspended carefully by a piece o f fine silk,
free from torsion, and descending through a hollow piece of cane,
w ith a microscope w ith intersecting wires for the reading of the
finely-graduated scale. T he observations may be calculated, when
necessary to compare them w ith those of any other instrum ent,
by noting, th a t the distance from th e point o f suspension to the
scale is 12.95 centimetres, and th a t each line of th e scale is equal
to 0.25 of a m illim etre: for, by dividing th e form er quantity by
th at of the daily movement, th e quotient will be th e tan gent of
the daily variation in minutes. T he results o f my observations9 at
Madeira are, th a t the greatest variation is a t 8 a.m. and the least
at 2 p .m .; and th a t th e variation decreases w ith th e tem perature,
being least in the coldest season. I hope to make a more regular
series o f observations and under more favourable circumstances a t9
* Gambey, who furnished Mr. Ritchie’s, asked me from 1500 to 2000 francs. ™
• Movement from 8 a.m., to 2 p.m.*, to 0 p.m.pf'rom 6 p.m., ta'8 a.m.
lines lines lines
2 2 — ^2 3 ^. 1.83 west + » .9 , east . 1 east
2 .3 ' ■ o ' ! J ) ^ j m i ;
2 1 — 2 5 I t ® 1 « " 0 . . : g J „ 1
2 5 ■ .8 i f !
2 f e - 2 ? . • 4 „ . t A m i
from 8 a.m., .to 22 p7 . mB . October 2»83th ,. 1| W., ; 29, th, (t.'. if r 30tfi, Ij W. 31st,
If w. November i / l y W: 4th, IJ W. 6th, 1 W. 13th, 1 W. 14th, ) W.
15th, J W. 16th, JW. 18th, IJ WV 19th, 1J W. 20th, D W. 2iet, J W.
22nd, i W, 25th, J W. 26th, J W. 27th, J W. December 5th, J WV: 6fh, J W.
7th, i W. - 14th, 1 W. 16th, J W„ .17tli,| W. 20th, I ff.. 28th,|Ay.
' p 1701 Coetlogon, 4° W. 1720 Laval) 8° 15' W. " 1758 Howe, 15°i2'W.11 1761
Bishop, 16° W. 1769 Fleurieu,. ,15>° -W.; H. M.SirLowestofif, 16° 30'0Vy,; ,1788
Johnston, 18 W. .‘.'01 .q .11 .i vara'AO v: