24 
SCIENCE. 
tall)- along with great swiftness, so as to strike the surface 
skimmingly and travel along with the motion compared 
familiarly to the flight of ducks and drakes. I believe that 
when a bird has given to its body, by a few powerful pro- 
pulsive efforts, a rapid forward motion, the resistance of 
the air resulting from the combination of perfect balance 
and swift forward motion suffices to explain all the phe- 
nomena of this floating movement. And I believe that if 
ever the art of flying — or rather of making flying machines — 
is attained by man, it will be by combining rapid motion 
with the power of perfect balancing. 
GENERAL NOTES. 
Instrumental Substitute for Singing in Birds. — The 
peculiar sound which the Lesser Spotted Woodpecker 
(Ficus minor) makes upon trees by the action of its bill is 
extremely curious. It is quite certain that this habit has 
nothing whatever to do with the quest for food. The bird 
selects one particular spot upon the trunk or bough of a 
tree, which spot is naturally sonorous from the wood being 
more or less hollowed by decay. The bird returns to this 
precise spot continually during the day, and produces the 
sound by striking the wood on the spot with its bill, the 
stroke being repeated with a rapidity which is really incom- 
prehensible ; for it quite eludes the eye. It is effected by a 
vibratory motion of the head ; but the vibrations are so 
quick that the action looks like a single stroke. After short 
pauses this stroke is again and again renewed, sometimes 
for several minutes together. During each interval the 
woodpecker looks around and below with evident delight, 
and with an apparent challenge of admiration. The beauti- 
ful crimson crest is more or less erected. 
The whole performance evidently takes the place of the 
vernal song in other birds, and it is probably the only case 
among the feathered tribes in which vocal is replaced by 
instrumental music. 
The nest is not usually in the same tree, but similai spots 
are selected on several trees in the neighborhood, and as 
the sound is very loud and heard a long way off, the hen 
bird, when sitting, is serenaded from different directions. 
The above observations on the substitution of instru- 
mental methods for singing among woodpeckers are highly 
interesting, and were made by the Duke of Argyle, and re- 
corded in Nature. 
Rusty Gold is the term applied to placer gold which 
escapes amalgamation in hydraulic and sluice washings. 
This is an old difficulty with miners, but the matter has 
never been thoroughly understood or properly investigated. 
Recently Mr. H. G. Hanks has read a paper on the subject 
before the San Francisco Microscopical Society. Under 
the microscope the particles of the sample he examined had 
a dark brown color, showing in some cases nearly white 
silica in irregular imbedded fragments, forming a com- 
pound cement. Some particles were wholly, others partly, 
coated. Placed in mercury the pieces wholly coated were 
acted on, those only partially so became amalgamated to the 
extent to which the gold was unprotected. The coating was 
found to be brittle. When pieces were struck with a ham- 
mer the coating scaled off, after which amalgamation took 
place without difficulty. On boiling some of the rusty gold 
in hydrochloric acid the coating was decomposed, silica 
separating, the acid acquiring a golden yellow color, and 
giving a strong reaction for iron, the gold being left clean 
and bright. Mr. Hanks appears to have refrained from 
drawing any conclusions, and further investigation appears 
desirable. 
Yeast. — A writer suggests that by a little study the large 
amount of “ pressed yeast,” which is now a by-product in 
most breweries, might be made into a profitable manufac- 
ture, similar to the German barm or yeast, which always 
commands a ready sale at a high price. He says that in the 
preparation of pressed yeast for brewing purposes we must 
first of all get rid of the saccharine matter if we want it to 
keep, as that would cause it to ferment and spoil, and also 
the bitter flavor, which can be accomplished by washing in 
a large volume of cold water. But while the washing pro- 
cess answers well in one sense, it unfortunately dissolves 
out the mineral matter of the yeast, which is necessary for its 
reproduction. The necessary conditions requisite for 
vigorous growth are a certain amount of sugar, soluble 
albuminoids (or an ammoniacal salts), oxygen of the air, and 
mineral matter, phosphoric acid being absolutely necessary. 
Polychrome Printing. — This is an invention to obviate 
many of the drawbacks to chromo-lithograph)' which en- 
tails a large number of separate printings, the drying after 
each impression, the “registration,” and the many expen- 
sive stones which have to be kept idle. The new process 
of Mr. White, of Paris, is a method by which all the colors 
of a chromo-lithograph may be produced at one im- 
pression. 
The pigment for the ground color is placed in a frame, in a 
solid block, and the design traced upon it. All the parts 
which do not form the ground color, are then cut out, and 
the spaces thus left are then filled by pouring in hot liquid 
pigments corresponding to the colors or shades required 
to be produced. When cold the recently added color is 
trimmed off with a knife, and another poured in, until the 
whole is built up. When complete the mosaic is placed in 
a press and the surface shaved by a knife, so as to make it 
true and level, and when moistened with suitable chemi- 
cals, it is ready for use. The impressions are clear, per- 
manent and pass through the fabric. 
Re-productions by this process of the farfamed Gobelins 
and Aubusson tapestries, are said to have deceived dealers 
and connoisseurs. 
American Olive Oil. — We notice in the Mining and 
Scientific Press , a formula for making Olive oil on a small 
scale, as produced in California. Compare this with a 
description in the Pharmaceutische Handelsblatt of the man- 
ufacture of Olive oil in Southern France. 
In California they grind the olives before pressure. This 
appears to be an error, they should be crushed between two 
stones, turning against each other vertically. We can quite 
understand that crushing leads to quite different results to 
grinding. In cider producing countries in Engiand apples 
are prepared for cider, in the same manner that the French 
prepare their olives for oil, by grinding them under revolving 
stones. Cider thus prepared will keep for years and improves 
with age, some say on account of an essential oil expressed 
from the apple pips. In America, cider is made from crushed 
or chopped apples, and possesses neither the flavor nor the 
keeping properties of that produced in Devonshire or Here- 
fordshire, England. 
There is another point which may be important on the 
“ Rhone.” The oil when filtered is stored in stone vessels ; 
on the Pacific they use tin cans. 
Temperature of Flames. — Signor F. Rosetti has made 
the temperature of flames the subject of a series of investi- 
gations. For this purpose he has made use of the calorimeter 
of his own invention. The maximum temperature of a 
Bunsen flame he has found to be 1360° C. (2480° F.) obtained 
by the combustion of one volume of gas and two and one- 
fifth volumes of air. The admission of either a greater or 
less quantity of air reduces the temperature. Changes in 
pressure have but a slight influence on temperature. The 
flame given by gas, diluted with its own volume of nitrogen, 
shows a temperature of 1180° C. (2156° F.), and diluted 
with three volumes of nitrogen, 1040° C. (1904° F.). The 
same degrees of dilution with carbonic acid show, respec- 
tively, noo° C. (2012 F.) and 780° C. (1436° F,). Among 
other temperatures noted were the following : From Locatelli 
lamp, 920° C. (1680° F.) ; stearin candle, 940° C. 
(1724 0 F.) ; petroleum lamp with chimney, 1030° C. 
(1886° F.) ; the same without chimney, illuminating part, 
920° C. (1688 0 F.) ; sooty envelope, 780° C. (1436° 
F.) ; alcohol lamp (alcohol, .912), 1170° C. (2138° F.) ; ditto, 
(alcohol, .822), 1180 0 C. (2156° F.). The difference in the 
heating power of alcohol resulting from widely differing 
percentages of water is considerable. 
The suggestion made by the Journal of the Telegraph 
to designate a message sent by telephone as a P honogram 
appears to meet with favor in the English electrical journals. 
