Vol. XXIV. No. 2.] 
POPULAE SCIENCE NEWS. 
21 
of steam, but the masses of lava and scorias in 
mid-air are well shown, and indicate the 
quickness of the exposure. The picture was 
taken by a French amateur, M. Luys, on the 
27th of September last. 
Fig. 2 is an excellent view of aman in the 
middle of a high jump. The remarkably 
awkward position of the bodv is noticeable, 
and shows how easily the eye is deceived by 
quick movements. No artist would venture 
to draw a man in such a position as a truthful 
representation of the attitude in jumping, but 
the eye of the camera cannot be deceived, 
even by the most rapid movements. 
Fig. 3 is a reproduction of a photograph 
made without any lens, a metal plate pierced 
with a hole 3-10 of a millimetre (i-ioo of an 
inch) taking its place. The time of exposure 
in a good light was i minute, 18 seconds. A 
sheet of pasteboard may be substituted for the 
metal plate. 
Although the "pin-hole" objective cannot 
replace the usual lenses in all cases, it has 
some advantages over them besides its cheap- 
ness and portability. Spherical aberration 
is avoided, the focal distance can be varied at 
pleasure, and in copying engravings and 
drawings in line or stipple, a very soft and 
pleasing picture is obtained, in which the 
lines or dots are blended together, and the 
details of the artist's work are not so unpleas- 
antly prominent as when the copy is made by 
a regular photographic objective. 
This method is worthy the attention of 
amateurs, and, after a few experiments in 
regard to the time of exposure, very satisfac- 
tory results can be obtained. It is important 
that the edges of the hole be perfectly sharp 
and clear, as the presence of a fringe of fibres 
of pasteboard or metal %\ould have a very 
injurious effect upon the finished picture. 
The, engravings are reproduced from 
La Nature. 
Canary-seed is composed of albuminoids, 138 
percent.; fat, 5.4; extractives, 50.7; indigestible 
fibre, 8.2; ash, 6.8; and water, 15.1. 
[Original in Popular Scunrf y ws.} 
THE SCIENTIFIC KNOWLEDGE OF THE 
ANCIENT GREEKS AND ROMANS. 
BY JOHN C. ROLFE, PH. D. 
III. 
MAGNETIS.M AND ELECTRICITY. 
Oi'R word magnetism is derived from Magnesia, 
the name of a town of Lvdia in Asia Minor. In the 
neighborhood of this place there was found a kind 
of stone, variously called Magnesian stone, Ljdian 
stone, stone of Heracles, and Siderite, which was 
observed to have the power of attracting iron. This 
stone, our loadstone (or, more properly, lodestont), 
was known to the Greeks as early as the fourth cen- 
tury before our era. According to Pliny, the Ro- 
mans knew four other localities which furnished the 
mineral: Magnesia in Thessaly, (to which our Eng- 
lish dictionaries erroneously refer as the place from 
which the name was derived), Ethiopia, Boeotia, 
and the Troad. Plato observed that the armature 
of a magnet itself became magnetic; and Lucretius, 
in his great poem on Nature, speaking of the lode- 
stone, says: "It often produces a chain of rings 
hanging down from it. Thus you may sometimes 
see five and more suspended in succession and toss- 
ing about in the light breeze, one always hanging 
down from the one above it and attached to its 
lower side, and each one in turn from the other ex- 
periencing the binding power of the stone, with such 
a continuous current the force flies through all." 
He explains the attraction by assuming the existence 
of an etherial force which poured forth from the 
lodestone or magnet itself, and permeated the pores 
of the magnetized object. Plutarch appears to ex- 
plain the phenomenon on the same principle. The 
magnetic power of the earth itself and the 
phenomena arising from it were, in spite of some 
wild theories to the contrary (it has even been 
claimed that the ancients were acquainted with 
the mariner's compass), completely unknown in 
that day. There were, however, stories of all kinds 
suggested by the power of the lodestone, the best 
known being that of the " magnetic mountain," 
which drew the iron nails from the planks of ships 
that came too near it, and caused them to fall to 
pieces. Ptolemy, the geographer, gave the exact 
latitude and longitude of this remarkable mountain, 
whose existence was firmly believed in. 
Still less did the ancients know o{ electricity. It 
was known from the time of Thales, who lived at the 
beginning of the sixth century B. C, that electron, 
when rubbed, had the property of attracting light 
objects. What is meant by electron in this con- 
nection is not certainly known ; amber, a mixture of 
gold and silver, tourmaline, a certain enamel, 
and platinum are some ol the conjectures of those 
who have discussed the question. However this 
may be, it was afterwards learned that amber was 
the best material for generating this kind of 
electricity. This attraction was personified by the 
imaginative Greeks. They spoke of a soul in the 
amber, as the Chinese physicist Kuo-pho did in his 
Poem in Praise of the Magnet. Plato's view was 
that the amber contained a flame-like essence, but 
gave it out only when the pores of its surface were 
opened by rubbing. This essence, when given out, 
had the same action as the magnet, but. by reason 
of its lightness and weakness, could attract only the 
lightest and driest substances. Pliny, too, speaks 
of a flame which pours out of amber. The con- 
nection of this frictional electricity with the external 
manifestations of atmospheric electricity, and with 
the shocks given by electric fishes (found in the 
Mediterranean and Red Seas), was never suspected 
by the ancients. 
IV. — CHEMISTRY. 
There enn be no question that some of our efctmi- 
cal experiments may lay claim to a very high anti- 
quity. According to Plutarch, whose etymology is 
approved by no less an authority than Alexander 
von Humboldt, the Greek word for chemistry, from 
which our own word comes, was derived from an 
Egyptian word, l<emi, originally meaning Hack, 
which was later a designation of the whole land of 
the Nile ; so that chemistry was synonymous with 
the hlack art! The first known Greek chemist 
(more properly a metallurgist) was Theophrastus, 
who lived in the fourth century before Christ. In a 
a book of his On Minerals he treats of the extraction 
of metals from the ore, and describes the various 
compounds which were formed in the process. 
Among these are white lead and verdigris, which he 
states to be earths, expressly distinguishing them 
from stones or minerals. 
Unfortunately this is the only work on chemistry 
written before the Christian era which has come 
down to us, although we know from references of 
Pliny that such books existed. Their loss is partic- 
ularly to be regretted, because it is possible that 
they might have thrown some light on the subject 
of polychromy, by telling us what aid the Greeks 
derived from chemistry in the preparation of the 
colors with which they decorated their statues and 
temples, and ornamented their walls with paintings. 
The encaustic painting of the Greeks has been 
especially discussed. Cato the Censor, who has 
already been referred to in these papers as having a 
practical knowledge of an important principle of 
heat, expresses some remarkably sound views about 
the rusting or oxidizing of metals under the in- 
fluence of the air, and upon the evaporation of 
water from springs to produce salt. 
The writers of the first century of our era bear 
witness to the chemical progress of earlier times. 
We find from their reviews of the past achi«vements, 
that various chemical preparations were used in 
medicine, especially in the composition of salves, 
and that alloys and amalgams of many kinds were 
familiar. He distinguishes the oxides of copper, 
lead, and zinc from one another. The only acids 
that appear to have been used are vineger (acetic 
acid) and sulphuric acid ; to the former was 
attributed a dissolving power far greater than it 
really possessed. In his passage of the Alps, Han- 
nibal, for example, is said to have dissolved rocks 
which barred his progress by the agency of vinegar. 
The process of distillation was used by the an- 
cients. Aristotle refers to this operation, which is 
clearly described by later writers, together with the 
retort and the rest of the apparatus. The progress 
in the knowledge of alloys is seen in the Roman 
coins of small denominations. These at first were 
made simply of copper, but from the time of Corn- 
modus they were composed of bronze with a vary- 
ing proportion of zinc. 
Soaps were known to the ancients, but were 
merely mechanical mixtures, not chemical. One of 
the supposed soaps found at Pompeii proved ta be 
nothing but fuller's clay. 
Alchemy began in the first century of our era, and 
the atomic theories of the philosphers are said to 
have led to the attempt to change the baser metals 
to the nobler ones. Towards the end of the fifth 
century this pseudo-science became very popular, 
and there were numerous guilds of alchemists at 
at that time. The prolific writer, Hermes Trisme- 
gistus, wrote a book called Tabula Smaragdina, 
professing to teach the art of making gold, which 
was translated at Nuremberg in 1541. 
In the concluding paper of this series the remain- 
ing departments of science will be briefly considered. 
Errata.— In the preceding paper Boethius was 
misprinted Bcethius, and Ptolemaius (thrice) as Ptol- 
enteit^fs. 
