Fan. 27, 1870] 
converge into an unvisited lake west or south-west of this.” If 
the expression ‘‘ one water” here means that these two lakes are 
united by an extension of one into the other, and not by a river, 
then it is evident that the river and lake chain under considera- 
tion can never flow up to join either of them after having passed 
down through the rent in the Mountains of Rua; if it means 
that these lakes are joined together by a river, still the small 
difference in height between that computed for Lake Tangan- 
yika by Mr. Finlay, of 2,800 feet (afterwards so curiously con- 
firmed by Livingstone’s height of Lake Liemba), and that found 
for the Albert Nyanza by Baker, would not give a sufficient low- 
ness to the latter lake to allow this river to flow down to it 
through the five degrees of latitude which separate its outfall 
from the Mountains of Rua, from the southern end of the Albert 
Lake. Dr. Livingstone’s statement in his letter above quoted 
from Ujiji, that the head waters of the Tanganyika and Albert 
Lakes are 300 miles south of that place, is not at all opposed to 
the view that the Chambeze River and its lake chain may join 
the Congo, for the streams which flow into his Lake Liemba 
may rise at this distance from Ujiji. In this case the sources of 
the Nile would be side by side with those of the Congo; and the 
man who has the claim to be called the greatest explorer that 
the world has ever known, has the double honour of having 
solved the two greatest of African problems. 
74, Strand, W.C. KEITH JOHNSTON, Jun, 
Physical Meteorology 
ASSUMING with your correspondent that there is an ascending 
current in the heart of a cyclone, no doubt latent heat will play 
its part. I presume, however, your correspondent does not 
imagine that air is ever actually heated by such means to 
370 F. 
Suppose, for instance, that two cubic feet of saturated air, 
both at thirty inches pressure, but one at the temperature 32° F. 
and the other at the temperature 90° F., become mixed. 
The cubic foot at 32° F. will contain 2°37 grains of vapour, 
that at 90° F. 14°50 grains. Hence, after mixture the average 
weight of vapour in unit of volume will be 8°43 grains. This 
would saturate a temperature = 71°7° F, But this is greater 
than the mean between the two temperatures or 61° F. There 
will, therefore, be hardly enough heat to keep the mixture at 
71°°7 F. and prevent deposition. 
On the other hand, we cannot imagine the temperature of the 
mixture to fall as low as 61° F. 
The temperature of the mixture will therefore, I presume, be 
greater than 61° and less than 7177". ; 
B. STEWART 
Veined Structure in Ice 
Few men haye had better opportunities of examining glacial 
phenomena than Mr. Whymper, and his explanation of the veined 
structure is certainly an ingenious one. I venture, however, to 
doubt whether it can be regarded as generally satisfactory, 
although, possibly, it might explain some isolated cases. 
The following, which, so far as my experience goes, are com- 
mon facts in glaciers, appear to me difficult to reconcile with his 
explanation. 
(1.) One common case in which the veined structure becomes 
conspicuous is after the glacier has been pressed into a narrower 
channel than has been occupied by its weve. The structure 
planes are then roughly parallel to the sédes of the channel. Dr. 
Tyndall has pointed this out in his ‘* Glaciers of the Alps,” p. 
387, and I have frequently observed the same thing myself. 
Three instances occur to me at this moment: one on the Gorner 
Glacier, under the Gorner Grat ; another in the middle part of 
the Glacier de la Pilatte (Dauphine); a third on the upper part 
of the Mer de Glace. Did I search through my note-book I 
have no doubt I could find plenty more. If now, say in the 
second example, the veined structure was due to the crevasses in 
the ice fall below the Col du Séle, surely its planes would hardly 
be twisted through a right angle in the comparatively short dis- 
tance intervening between the ice fall and the rocky spur from 
the Créte des Boeufs Rouges which causes the ‘‘nip.” Moreover, 
if the planes have been turned by the unequal motion of the 
centre and sides of the ice stream, ought we to find them so uni- 
form in direction as they now are, often extending with a very 
general parallelism over the greater part of the glacier ? 
(2.) If the veined structure is the result of healed crevasses, 
how are we to explain the great number of these plates of different 
coloured ice on glaciers which are not remarkable for very nume- 
NATURE 
Sod 
rous crevasses. For example, on the Roseg Glacier, near Pon- 
tresina, these plates of blue and white ice alternate with each 
other for at least several hundred yards as you walk up the 
glacier, and are commonly only an inch or so thick. I have in 
my notebook a diagram of a piece to exhibit the weathering of 
the two kinds of ice, in which are shown five plates, three blue 
and two white. One of the former is about an inch thick, and 
all the rest are thinner. Each of the white is about half an inch, 
and I remember that this was a fair sample of most of the ice 
near, If, then, the crevasses, from whose healing this platy 
structure has resulted, were formed simultaneously or in close 
succession, how are we to explain the thinness of the white 
portion, its layers being, if anything, thinner than the blue? 
Crevasses are not usually so near together as this, and if they 
were not thus formed is it probable that the plates would be so 
produced as to be, for about as far as one could trace them, 
parallel one to another, so accurately that my diagram looks like 
a bit from a cliff of midland lias? 
Cambridge, Jan. 7 T. G. BONNEY 
Personal Equation of Astronomical Observers 
In the number for November 18, 1869, of NATURE, “J.” asks 
if an experiment has hitherto been tried to ascertain the value of 
the personal equation of astronomical observers. The fact is, 
that it has been tried in different manners, as by Mr. Wolf in 
Paris, and Mr, Hirsch in Neuchatel, but first of all by Dr. F. 
Kaiser, Astronomical Professor, and Director of the Observatory 
of Leiden. The apparatus of Prof. Kaiser was first constructed 
in 1851, but was afterwards highly improved, so that it is 
fitted equally well for observations with or without the 
chronograph. 
A description of the method and apparatus of M. Kaiser is to 
be found in the “‘ Archives Néerlandaises des Sciences exactes et 
Naturelles,” vol. i. p. 194, and of the improved one in the reports 
and communications of the Royal Academy of Science of the 
Netherlands (Verslagen en mededeelingen der Koninklijke 
Academie van Wetenschappen), Second Series, vol. ii. ; the 
former is written in French, and titled: ‘‘Sur la détermination 
absolue de lerreur personelle dans les observations astrono- 
miques ;” the latter, in German ; ‘‘ Uebereinen neuen Apparat zur 
absoluten Bestimmung von persdnlichen Fehlern bei astro- 
nomischen Beobachtungen.” H. Von DE SrTapt, Ph.D. 
Arnheim, Netherlands, January 3 
Anatomical Lectures to Female Medical Students 
I HAVE great pleasure in hearing that the Professors of 
Anatomy in Scotland have not all forgotten that women ought 
to be treated with some degree of chivalry. 
Professor Struthers, of Aberdeen, and Professor Bell, of St. 
Andrews, hearing that the five ladies who are studying at the 
Edinburgh University are excluded from the opportunity of 
studying anatomy there, have severally offered their services as 
instructors. Many a lady will rejoice that the numbers of those 
willing and ready to help in the good cause of fuller knowledge 
for women are increased by two professors, who have bravely 
come forward with much moral courage and chivalrous feeling, 
Edinburgh, Jan. 22. A NoNn-MEDICAL WOMAN- 
NOTES 
THE Physical Section of the Academy of Sciences at their 
last meeting recommended Professor Kirchhoff, of Heidelberg, 
to fill the place of correspondent of the section, vacant by the 
death of Principal Forbes. The other candidates were MM. 
Angstrom, Billet, Dove, Grove, Henry (of Philadelphia), Jacobi, 
Joule, Lloyd (of Dublin), Riess, Stokes, Tyndall, Volpicelli, and 
Sir William Thomson. 
In our statement last week that ‘‘the Senate of London Uni- 
versity has proposed to establish a Faculty of Science,” ‘‘ London 
University” should have been “ University College, London ;” the 
fact being that the Senate of the University of London—in ad- 
vance of every other university of the kingdom—established a 
Faculty of Science e years ago ; constituting, at the suggestion, 
and with the advantage of the advice, of the ablest men of science 
in this country, a scheme for graduation in science, which has 
continued in efficient operation from that time to the present. 
And we may add that in the new building of the University the 
