440 
WALOR FE 
| Marcu 11, 1897 
trace, doubtless due to tremor of the mirror, and, though not | 1892 Captain V. Bottego obtained no less than eighteen speci- 
so well marked, yet quite similar in character to the gaps 
described in a previous letter (NATURE, No. 1410, November 5, 
1896) ; at 5.32 p.m. another abrupt movement to the north, and 
a similar one at th. 20m. after midnight. 
movements have been compared with the mean of two measures 
of the sensitiveness of the instrument, and show tilts in the 
mirror frame of 1°6, 1°1, and 1°3 seconds of are respectively. 
In each case the mirror returned to the normal position slowly 
after a period of from 2 to 4 hours. 
On the other date given by Prof. Milne—February 13—there 
is only a slight trace of irregularity in the curve, consisting of a 
bend towards the north at Sh. 2m. a.m., the mirror returning to 
its original position three hours later. 
On dates more recent than those to which Prof. Milne calls 
attention, several disturbances have been recorded here. Of 
these the most strongly marked are : an abrupt north movement 
on February 16 at 8 p.m., and another on the 17th at 3 a.m. 
On the 18th there is a similar movement to the south at 6.15 
The three abrupt | 
a.m., followed by two smaller oscillations in the opposite | 
direction, the three covering a period of 14 hours. On February 
19 there are two well-marked gaps, precisely similar in character 
to those described in the letter above referred to. 
Tuomas HEATH. 
Royal Observatory, Edinburgh, March 2. 
| climbers. 
mens of that most singular rodent, /eterocephalus glaber, in one 
day. at the Wells of Herrer, near Archeisa, in North Somaliland. 
Sixteen specimens, well preserved in alcohol, were forwarded by 
him to Marquis Giacomo Doria, and have been distributed to 
various museums through the learned Director of the Museo 
Civico of Genoa. In his book (‘‘ Il Giuba esplorato,” pp. 38-41, 
Roma, 1895) Captain Bottego figures the Heterocephalus, and 
also one of their colonies of singular conical mole-hills. 
Florence, February 24. Henry H. GIGUIOL!. 
THE CAUCASUS. 
ITTLE though the methods and spirit of sport have 
in common with those of science, each subject is 
greatly indebted to the other. Our knowledge of the 
habits of big game is mainly due to hunters ; and for the 
first great advances in mountain cartography and in the 
study of high mountain regions, we are indebted to 
In the early days of the Alpine Club some 
of its members, at the suggestion of John‘ Ball, placed 
instruments on summits that were accessible only to 
Fic. 1.—Ushkul. 
The Origin of Manna. 
THE note in NATURE, p. 349, concerning the ‘‘ manna,” 
reminds me of a passage in Daniele Bartoli’s ‘* Asia.” 
Speaking of the island of Ormuz—which is described as one 
of the places in the world worst supplied in even commonest 
necessities of life, and scarcely having any water—the historian 
tells us that ‘‘not even thorns and briars could grow on its 
barren soil ; no animals or birds (sc) are seen there all the year 
round, but every morning a dew falls which congeals into 
grains, has a very sweet taste, and is called ‘ manna.’” 
Now, tamarisks affect sandy soils or brackish shores; and as 
T. mannifera grows in Arabia, it may be that the exudations 
from the plants were blown from Oman, on the eastern shore of 
Arabia, across the Persian Gulf; or, perhaps, from the nearer 
coast of Persia. This would seem to confirm the belief that 
manna is the product of the tamarisk, and not of a lichen. 
Tooting College, S.W., February 26. B. Timorny. 
‘*Heterocephalus glaber” in North Somaliland. 
In reference to the note given in Narure (vol. lv. p. 301) on 
the mammals collected in North-east Africa by Dr. Donaldson 
Smith, it may interest some of your readers to learn that in October | 
NO. 1428, VOL. 55] 
trained mountaineers, and thus obtained meteorological 
records much wanted at that time. Subsequently, 
another group of members of the Alpine Club turned 
their attention to the Caucasus, where their explor- 
ations resulted in the first accurate knowledge of its, 
lofty summits and its great snow-fields and glaciers. 
| Of the Alpine climbers who have taken part in this work, 
Mr. Douglas Freshfield was one of the earliest, was the 
best qualified as a geographer, and has been by far the 
most persistent. His “Central Caucasus and Bashan” 
(1869), which has taken place as an Alpine classic, 
| helped to rouse the first interest in England regard- 
ing the former mountains; and now, after thirty years’ 
further work has been done, he has collected the 
principal results imto a monograph, which is un- 
questionably the best illustrated book in the literature 
of mountaineering. 
Mr, Freshfield begins with a chapter on the “ Dis- 
1 “ The Exploration of the Caucasus.’ By Douglas W. Freshfield. With 
illustrations by Vittorio Sella. Imp. 8vo. 2 vols. Pp. xxiii +278; pp. 
x +295; with 3 maps and 76 full-page illustrations, and 2 mountain 
panoramas. (London: Edward Arnold, 1896.) 
