SCIENCE. 
69 
natives of South Africa, and those of some of the Sunda 
Isles esteem dragon-flies a great delicacy, catching them, 
according to Wallace, on birdlimed twigs. Though there 
can be comparatively little nutriment in the soft bodies of 
insects, yet there is no reason for the horror with which 
they are regarded, as articles of food, by the Aryan races. 
A fancy for the flavor of the Rocky Mountain locust would 
go far toward decreasing the devastation of that dreaded 
pest. 
Some of the marine worms are accounted delicacies by 
certain tribes, but the greater part of the varied forms be- 
longing to the sub-kingdom must be regarded, so far as 
they are useful to man at all, as only indirectly so through 
their consumption by animals he feeds upon. The same 
may be said of the Protozoa, which, swarming in countless 
numbers in sea and river, lake and marsh, furnish food for 
the creatures above them. 
Putting aside all question of protection or preservation 
of plants and animals now used as food, the examples ad- 
duced are sufficient to show that the range of foods might, 
with advantage, be greatly extended. 
Much remains to be learned respecting the diseases and 
bodily states of cold-blooded animals and of the inverte- 
brata before we can use them for food with the same confi- 
dence with which we eat beef, mutton or poultry. The 
diseases of the higher animals are, to a great extent, similar 
to our own, and we have learned how to discriminate ; but 
we do not recognize the diseases of fishes, crabs and shell- 
fish. The stories of poisonous fish probably arise from this 
source. Every year we hear of cases of poisoning, well 
authenticated, from eating mussels, lobsters or other Crus- 
tacea, or mollusks, which are usually healthy food. All 
these creatures are subject to diseases which we have not 
yet studied, and it may be that at certain seasons, such as 
immediately after reproduction, some of them are unfit for 
food. This is one well-grounded cause of prejudice, but 
one which will be removed as our knowledge of the lower 
forms of life extends. 
The animal and vegetable world furnish us with other 
things besides food. Materials of other descriptions fur- 
nish, by their manufacture, a means of procuring food to 
some, while the articles manufactured are of use to all. 
Commerce, which has made us familiar with foods pre- 
viously unknown, has helped us still more in this direction, 
yet when we consider the great variety of vegetable and 
animal life, we cannot but believe that much more remains 
to be discovered, or, at least, utilized. 
Other nations, many of them but semi-civilized, others 
barbarous, have, in these things, been our teachers. As 
maize and potatoes were known to the Indians before we 
learned to use them, so was P hormiumtenax to the Maoris, 
and cotton to the Hindoos and Chinese. 
When it is remembered what vast industries depend upon 
the supply of fibrous plants, and, that a fibre with different 
qualities, as it could be applied to new uses, would start a 
new branch of trade ; when we see how extensive are the 
manufactures carried on from gum-resins like caoutchouc, 
or gutta-percha, we must acknowledge that the discovery of 
a fiber or a resin with new uses would furnish a livelihood 
to many additional workers. Take paper for example. 
Until lately this article was made from linen rags, but as 
the supply of that material fell short of the demand, cotton 
waste, siraw, the Yucca plant, and other vegetable materials 
came into use, and it is evident that it can be made from 
almost any fibrous substance reduced to a pulp. Few are 
the plants that cannot be utilized by man. If valueless for 
food or for building purposes, a fiber, a gum, an essential 
oil, a medicinal product, may be found in most. 
The constantly-increasing stock of geographical and bo- 
tanical knowledge brings new materials into the notice of 
scientists, and the constantly increasing needs of mankind 
brings them slowly into public notice. The secretion lately 
found in Arizona, upon the blanches of Larrea Mexicana, 
and of another plant, may yet enable us to dispense with 
the imported lac from Asia. Chemically the two seem 
identical; practically the despised Indian, here again our 
teacher, has long ago proved its use in the mending and 
making of vessels for cooking purposes. 
Here is «. case of a new material furnished by the animal 
kingdom, for it appears almost certain that the secretion, 
like that of wax or honey, is elaborated by the insect from 
the juices of the piants it feeds upon. Insects, so little 
used for food, so terribly destructive to our food plants and 
annoying to our domestic animals, may yet yield to us many 
useful materials ; may yet prove in this respect among the 
most useful of organisms. Silk, honey, wax, gum-lac, 
cochineal, all are insect products, elaborated by insects 
from plants ; and the last two are the produce of coccidce, 
those destroyers of our orchards and orangeries. Does not 
this point a way to the utilization, in some cases, of our 
insect pests ? 
The higher animals may not furnish us with many addi- 
tional materials. Horn, hair, fur, wool, hides, feathers, 
bone, ivory, have their known uses. Improvement here is 
to be looked for rather in new uses for known materials 
than in the discovery of new ones. But the lower animals 
may yet yield us many useful substances. The great trea- 
sure house of the sea holds more than we have yer learned 
the use of. Shells, corals, the honey axes of soft-corals, 
and many other portions of marine animals, may be utilized 
for something more than show ; and other secretions maybe 
found as useful as those of the sepia. But though the 
number of useful species — useful either directly or indirectly 
— is so large that it includes probably the greater portion of 
existing organisms, yet some are far more useful than 
others, and some are directly injurious to more useful 
organisms. Such species need not be cultivated, except 
where they do not come into direct competition with more 
useful ones ; but their consumption or use by man would 
diminish their numbers and give room for the more useful 
forms, which are now often permitted by man, even in his 
own cultivated fields, to be crowded out by the less useful. 
— Scientific Press, Cal. 
Two eggs of the extinct great auk were sold by auction 
in Edinburgh recently, both being purchased by Lord Lil - 
ford, one at ^jioo, the other at 102 guineas, probably the 
largest sum ever paid for a single egg, with the exception 
of that of the moa, a single specimen of which was sold at 
the same place in 1865. for £200. 
Progress in Utilization of Solar Heat. — Since May, 
last year, M. Mouchot has been carrying on experiments 
near Algiers with his solar receivers. The smaller mirrors 
(0.80 m. diameter) have been used successfully for various 
operations in glass, not requiring more than 400° to 500°. 
Among these are the fusion and calcination of alum, pre- 
parations of benzoic acid, purification of linseed of oil, con- 
centration of syrups, sublimation of sulphur, distillation of 
sulphuric acid, and carbonization of wood in closed vessels. 
The large solar receiver (with mirror of 3.80 m.) has been 
improved by addition of a sufficient vapor chamber and of 
an interior arrangement which keeps the liquid to be vapor- 
ized constantly in contact with the whole heating surface. 
This apparatus on November 18, last year, raised 35 litres 
of cold water to the boiling point in 80 minutes, and an 
hour and a half later showed a pressure of eight atmos- 
pheres. On December 24 M. Mouchot with it distilled 
directly 25 litres of wine in 80 minutes, producing four 
litres of brandv. Steam distillation was also successfully 
done, but perhaps the most interesting results are those re- 
lating to mechanical utilization of solar heat. Since March 
the receiver has been working a horizontal engine (without 
expansion or condensation) at a rate of 120 revolutions a 
minute, under a constant pressure of 3.5 atmospheres. The 
disposable work has been utilized in driving a pump which 
yields six litres a minute at 3.50 m. or 1,200 litres an hour 
at 1 m., and in throwing a water-jet 12 m. This result, 
which M. Mouchot says could be easily improved, is ob- 
tained in a constant manner from 8 a. m. to 4 p. m., neither 
strong winds nor passing clouds sensibly affecting it. 
