April 14, 1870]| 
NATURE 
615 
The means of observations 1 and 3 and of 2 and 4 were then 
taken. The sun’s altitude was determined by a sextant and 
artificial horizon, immediately before and immediately after the 
observations of chemical intensity, the altitude at the time of 
observation being ascertained by interpolation. 
Tt was first shown that an accidental variation in the position 
of the brass ball within limits of distance from the paper, vary- 
ing from 140 millimetres to 230 millimetres, was without any 
appreciable effect on the results. One of the 134 sets of obser- 
vations was made as nearly as possible every hour, and they thus 
naturally fall into seven groups, viz. :— 
(1) Six hours from noon, (2) five hours from noon, (3) four 
hours from noon, (4) three hours from noon, (5) two hours from 
noon, (6) one hour from noon, (7) noon. 
Each of the first six of these groups contain two separate sets 
of observations, (1) those made before noon, (2) those made 
after noon. It has already been pointed out,* from experiments 
made at Kew, that the mean chemical intensity of total daylight 
for hours equidistant from noon is constant. The results of the 
present series of experiments proves that this conclusion holds 
good generally, and a Table is given showing the close approxi- 
mation of the numbers obtained at hours equidistant from 
noon. 
Curves are given showing the daily march of chemical inten- 
sity at Lisbon in August, compared with that at Kew for the 
preceding August, and at Para for the preceding April. The 
value of the mean chemical intensity at Kew is represented by the 
number 94°5, that at Lisbon by rio, and that at Para by 3133, 
light of the intensity 1°o acting for 24 hours being taken as 
1,000, 
The following Table gives the results of the observations 
arranged according to the sun’s altitude :— 
No. of Mean Chemical Intensity. 
Observations. Altitude. Sun, Sky. Total. 
° / 
TiS Gepch= SN 0'000 0°038 0'038 
Sh 5) al Ste ey 0'023 0°063 0'085 
ZEA ge EAN 0052 0*100 O'152 
ON ae ace WYO BE "100 O'1I5 O°215 
ROM eth gee 531 100, 0°136 0°126 0°262 
BAe con Ole (OS, O'195 O°132 0°327 
EDA ah O4)- TA 0°221 0138 0°359 
Curves are given showing the relation between the direct sun- 
light (column 3) and diffuse daylight (column 4) in terms of the 
altitude. The curve of direct sunlight cuts the base line at 10°, 
showing that the conclusion formerly arrived at by one of the 
authors is correct, and that at altitudes below 10° the direct sun- 
light is robbed of almost all its chemically active rays. The 
relation between the total chemical intensity and the solar alti- 
tude is shown to be represented graphically by a straight line 
for altitudes above 10°, the position of the experimentally deter- 
mined points lying closely on to the straight line. 
A similar relation has already+ been shown to exist (by a far 
less complete series of experiments than the present) for Kew, 
Heidelberg, and Para; so that although the chemical intensity 
for the same altitude at different places and at different times of 
the year varies according to the varying transparency of the 
atmosphere, yet the relation at the same place between altitude 
and intensity is always represented by a straight line. This 
variation in the direction of the straight line is due to the 
opalescence of the atmosphere ; and the authors show that, for 
equal altitudes, the higher intensity is always found where the 
mean temperature of the air is greater, as in summer, when ob- 
servations at the same place at different seasons are compared, 
or as the equator is approached when the actions at different 
places are examined. The differences in the observed actions 
for equal altitudes, which may amount to more than 100 per cent. 
at different places, and to nearly as much at the same place at 
different times of the year, serve as exact measurements of the 
transparency of the atmosphere. 
The authors conclude by calling attention to the close agree- 
ment between the curve of daily intensity obtained by the 
above-mentioned method at Lisbon, and that calculated for 
Naples by a totally different method. 
“On the acids contained in crab oil.” By William J. 
Wonfor, Student in the Laboratory of the Government School 
of Science, Dublin. Communicated by Dr. Maxwell Simpson. 
* Phil. Trans. 1867, p. 558. 
+ Phil. Trans. 1867, p. 555: 
Crab-oil is obtained from the nuts of a tree named by botanists 
Hylocarpus carapa and also Garafa Guianensis. The tree 
grows abundantly in the forests of British Guiana; the oil is 
prepared by the Indians, who bring it to George Town for 
sale. The oil is obtained from the kernels by boiling them for 
some time, and then placing them in heaps and leaving them for 
some days; they are then skinned, and afterwards triturated in 
wooden mortars until reduced to a paste, which is spread on 
inclined boards and exposed to the sun; the oil is thus melted 
out, and trickles into receiving vessels. 
As no investigation, so far as I have been able to ascertain, 
has ever been made of the acids contained in this oil, Professor 
Galloway, to whom I am indebted for the samples of the oil, 
recommended me to examine them, and the examination was 
conducted under his direction. The acid, when pure, presents 
the appearance of a white glistening radiated crystalline mass. 
The percentage composition obtained was as follows :— 
Garnbong sme ascaccetanesrescnees 
Hydrogen 
Oxygen) secs. Asstvowedsect wees. 
100°000 
These analyses agree very closely with the formula for palmitic 
acid, CygH5,04. 
Royal Geographical Society, March 28.—The president, 
Sir R. Murchison, in the chair. A paper was read by Sir 
Charles Nicholson, Bart., on Forrest's Journey in Western Aus- 
tralia ; Goyder’s survey of the neighbourhood of Port Darwin, 
and on the recent progress of discovery in Western Australia, and 
remarks on Papua or New Guinea. Intense interest had been 
felt in the fate of Leichhardt and his party, who were last heard 
of in 1849 S.W. of the Gulf Carpentaria ; a report was brought 
to the government of Swan River, of the existence of the remains 
of two white men and horses in the unexplored region N.E. of 
the colony. An expedition was fitted out, under Mr. Forrest, 
with whom Mr. Monger and Mr. M. Hamersley were associated, 
and the native Jimmy Mungaro acted as guide.. The place 
indicated was Koolanobbing, lat. 30° 53/ S., and long. 109° 14’ 
E. The expedition was exceedingly well managed, and the 
country was thoroughly examined. They left Newcastle April 
19, 1869; passed through a sandy country without grass ; water 
was scarce ; salt lakes nearly dried up were met with ; from the 
limit of Gregory’s exploration, 118 long., they travelled north ; 
found granite hills, with spearwood and acacias ; in May 5 they 
reached Lake Moore, and learned that the remains were those 
of horses which had been poisoned, having strayed from 
an out station; some unfriendly natives, who threatened 
to kill and eat the white men, were met with; several 
large dry salt lakes were discovered, one of which, named 
Lake Barlee, was conjectured to be 80 miles in length, 
the farthest point, 28° lat. 41’ S., and 122° 50’ E. long., was 
reached July 2nd. The country throughout of the same barren 
worthless character, granite hills, no grass, and scanty supplies 
of water. The return journey was made to north of Lake 
Barlee, westward to Bunnaroo, and southward to Mount 
Singleton on July 23rd; the result was that no traces of 
Leichhardt were found, and the country explored was_pro- 
nounced unfit for either pasture or agriculture. In the sea board 
districts and about Mount Singleton there was excellent land, 
all Western Australia wanted was population. Sir Charles 
Nicholson then proceeded to notice the recent survey of Port 
Darwin, in North Australia, which region, between 128° and 
138° E. long., and north of 26° S. lat., had been most un- 
reasonably annexed to South Australia. The South Australian 
attempt to open communication through the interior, and found 
a colony at Port Essington, had failed, and the colony had been 
abandoned. Port Darwin lies to west of Adelaide River, on 
northern coast, opposite Melville Island; it possesses a good 
harbour, a million acres of good land have been surveyed, fit 
for horses and cattle, not for sheep, climate from May to Sep- 
tember is good, then moist and hot; intercourse by sea between 
the Malays of Macassar and this port exists. Port Darwin has 
been recommended as a port for shipping horses for the Indian 
market, the central region is impracticable, but the route followed 
by M‘Kinlay from Northern Queensland is, in the opinion of 
Mr. Goyder, Colonial surveyor, the best; this, Sir Charles 
Nicholson thought showed that North Australia ought to form 
part of Queensland, Sir Charles gave a rapid réswmdé of the 
