Fuly 13, 1886] 
NATURE 243 
The collection from British North Borneo has many 
interesting exhibits, notably some remarkably fine speci- 
mens of gutta-percha and india-rubber a magnificent 
plank of the Sumatra or Bornean camphor-tree (Dryo- 
balanofts aromatica), the crystallised camphor of which is 
found deposited in cracks and fissures in the wood, 
occurring sometimes in very large masses; it is largely 
used by the Chinese, who prefer it to the ordinary camphor 
of commerce which is produced in their own country. 
Bornean tobacco is also a prominent object here, and 
is exhibited both in bundles of cured leaves as well as in 
cutform. A favourable report has been obtained of this 
tobacco, and it has been valued above the average of 
Sumatra tobacco, for which indeed it has been mistaken 
even by experts. 
In the Hong Kong Court the varied uses to which 
bamboos and rattans are put are largely represented ; the 
difference, however, in the character of the work to which 
the stems of these two classes of plants are applied is 
manifest at a glance, for while the rigid stems of the 
Bambusas are used for the rougher or coarser work, those 
of the pliable species of Ca/amus form the materials from 
which the finer basket-work, screens, &c., are manipulated. 
Various examples of the baker’s art in the form of biscuits 
are shown by the Hong Kong and China Bakery Com- 
pany, Limited, and it is stated, as an illustration of the 
capabilities of this bakery, that it can turn out 15,000 
pounds of ship biscuits or 10,000 pounds of bread per 
day. 
The British Guiana collection almost adjoins that of 
Hong Kong. Here, as might be expected from the extent 
of the forests of the colony and the abundance of large 
hard-wooded trees, timber takes a prominent place, and 
some magnificent specimens of the best known woods, such 
as mora (Dimorphandra Mora), greenheart (Vectandra 
Rodiwi), wallaba (Eperua falcata), and other well-known 
and useful timbers are exhibited. The heartwood of 
these timbers is described as “almost everlasting, the 
beams of old houses being good for over a hundred 
years in the most unfavourable circumstances of a tropical 
climate infested with wood-ants and other vermin.” 
Specimens of tibiserie fibre and hammocks made from 
it are here exhibited. This fibre, which is obtained from 
the young leaves of the Eta palm (Mauritia flexuosa), 
is of wonderful strength and tenacity, from it the 
natives make their strongest and most durable cords and 
hammocks. It is very easily obtained and in any quan- 
tity, and if better known in Europe might become a 
valuable article of commerce. A fine collection of medi- 
cinal and tanning barks are here shown, but unfortunately, 
like the woods from this colony, comparatively few have 
other than native names. In the catalogue of exhibits it 
is stated that “the medicinal barks are very varied; a 
few are well known, but the majority, having never received 
the attention of chemists or physicians, are as yet untried, 
but may possibly be found worthy a place in the Materia 
Medica. Fair quantities are exhibited, and will be dis- 
tributed to qualified persons who will undertake to report 
on their qualities. Most of them are common in the 
colony, and can be easily procured.” 
It is scarcely correct to say that the medicinal barks of 
British Guiana have never received the attention of 
chemists or physicians, for at the close of the Inter- 
national Exhibition of 1862 some twenty different medi- 
cinal barks of the colony were experimented upon and 
their effects tried in various cases by Mr. Charles Hunter, 
who was some time House Surgeon to St. George’s Hos- 
pital. The results of his experiments were embodied in a 
pamphlet, and published at the time by Messrs. Churchill 
and Sons of New Burlington Street, but we never heard 
that any of them came into use in this country, and it is 
to be hoped that better results may be obtained from the 
present collections. 
JOHN R. JACKSON 
WHAT IS A GLACIER 2} 
LACIERS have become so well known from the 
graphic descriptions of Carpenter, Forbes, Agassiz, 
Tyndall, and other explorers, that it seems unnecessary at 
this time to do more than call attention to a few of their 
more characteristic features by way of an introduction to 
what I have written concerning those now existing in the 
United States. 
The formation of glaciers in any region depends pri- 
marily on the fact that the amount of snow precipitated 
during a term of years exceeds the amount dissipated by 
melting and evaporation. In this manner snow-banks of 
broad extent are formed, the lower portions of which 
become compacted into ice. The change from snow to 
ice is known to result from pressure, and as ice is mobile 
under pressure, either by reason of its inherent plasticity 
or asa result of regelation, the weight of this mass tends 
to change its form, and it thus acquires motion, which 
takes the direction of least resistance. 
The essential characteristic of glaciers seems to be that 
they result from the consolidation of snow in regions of 
secular accumulation, 7.2. above the snow-line, and flow 
to regions of dissipation, z.e. below the snow-line. From. 
these primary conditions result a multitude of secondary 
phenomena. 
For convenience of reference we will divide glaciers 
into alpine and continental ; not that the two classes are 
always distinct and separable, but for the reason that 
typical examples of each are well characterised and capable 
of specific description. Variations occur in each class 
which may suggest minor subdivisions. 
The glaciers with which we are most familiar belong to 
the class that have their archetype in the mountains of 
Switzerland, and occur about high peaks, usually in 
amphitheatres or cvgues at the heads of high-grade 
valleys. The snow that accumulates on high mountains, 
especially in temperate latitudes, is frequently not com- 
pletely melted during the summer, and thus tends to 
increase indefinitely. The w#évé of a glacier is such a 
snow-field. The gorge or valley leading from every alpine 
amphitheatre furnishes an avenue of escape for the con- 
solidated 2évésnow, which is forced out through the 
opening, and flows for a greater or less distance as a 
stream of ice. Such in brief is the genesis of an alpine 
glacier. Every glacier of this class is divided into a 7évé, 
or snow-region, above, and an icy portion below. The 
line of demarcation is the szow-/ine. As compact ice 
occurs also beneath the #évé from which it is formed, this 
division of a glacier into two portions applies only to the 
surface. The division line, moreover, shifts with the 
seasons ; at times, perhaps for many years together, the 
true glacier ice may be concealed by a snowy covering. 
The zévé is composed of granular snow, white or grayish- 
white in colour, and comparatively free from dirt and 
stones ; below the snow-line the glacier is formed of both 
porous and compact ice, and is usually concealed more or 
less completely with rock-debris. From a distance these 
two divisions are frequently distinctly shown by contrast 
in colour. The stones and dirt that fall on the zévé sink 
more or less deeply into the snow and become buried 
beneath the next addition, and as the #évé becomes 
consolidated and acquires glacial motion, this debris is 
carried along in its mass. But the region below the weve 
being one in which loss exceeds supply, the snow and ice 
are melted, and the foreign bodies formerly held in the 
mass become concentrated at the surface, and are then 
carried along as moraines. Thus in the #cvé region the 
tendency is to bury foreign objects, and in the glacier 
proper to concentrate them at the surface. 
All the debris carried by glaciers may be designated in 
general terms as morainal material, but when arranged 
© Frcm Memoir on “‘Exi-ting Glaciers of the United States,” by Israel 
C. Russell. Reprinted from the Fifth Annual Report of the Director of the 
U.S. Geological Survey. 
