The
Natural History is generally divided into the organic plants and animals and the inorganic matter, although there are frequent digressions in each section. The encyclopedia also notes the uses made of all of these by the Romans. Its description of metals and minerals is valued for its detail in the
history of science, being the most extensive compilation still available from the ancient world. Book I serves as Pliny's preface, explaining his approach and providing a table of contents.
Astronomy found the distances to
Sun and
Moon The first topic covered is Astronomy, in Book II. Pliny starts with the known universe, roundly criticising attempts at cosmology as madness, including the view that there are countless other worlds than the Earth. He concurs with the four (Aristotelian) elements, fire, earth, air and water, and records the seven
"planets" including the Sun and Moon. The Earth is a sphere, suspended in the middle of space. He considers it a weakness to try to find the shape and form of God, or to suppose that such a being would care about human affairs. He mentions eclipses, but considers
Hipparchus's almanac grandiose for seeming to know how Nature works. He cites
Posidonius's estimate that the Moon is 230,000 miles away. He describes
comets, noting that only Aristotle has recorded seeing more than one at once. Book II continues with natural meteorological events lower in the sky, including the winds, weather, whirlwinds, lightning, and rainbows. He returns to astronomical facts such as the effect of longitude on time of sunrise and sunset, the variation of the Sun's elevation with latitude (affecting time-telling by sundials), and the variation of day length with latitude.
Geography In Books III to VI, Pliny moves to the Earth itself. In Book III he covers the geography of the Iberian peninsula and Italy; Book IV covers Europe; Book V looks at Africa and Asia, while Book VI looks eastwards to the Black Sea, India and the Far East.
Anthropology Book VII discusses the human race, covering
anthropology and
ethnography, aspects of human
physiology and assorted matters such as the greatness of
Julius Caesar, outstanding people such as
Hippocrates and
Asclepiades, happiness and fortune.
Zoology from the Archeological Museum of
Aquileia Zoology is discussed in Books VIII to XI. The entries begin with a discussion of terrestrial animals, taken to include mammals, reptiles, amphibians, and an assortment of mythological creatures recognised as real animals (e.g. dragons). The
elephant, and the
lion are described in detail, with accounts of behaviors, taming, and battles with bestiarii referenced. Other species are listed in relation to their geographic ranges, for example India and the far north. Domestic dogs, horses, and livestock feature prominently, with elaboration on their uses to humans, for example the types of wool produced by
sheep and the cloth created from them. From there, "the natural history of fishes" is outlined. Pliny identified all aquatic animals as "fishes", making distinctions between those "with red blood" (
cetaceans and traditional
fishes) and those "without blood", the latter classified between "soft fishes" (
cephalopods), those with "thin crusts" (e.g.
crustaceans and
sea urchins), and those enclosed with hard shells (e.g.
bivalves and
gastropods). As well, jellies are described with "bodies of a third nature" as a mix of animal and plant. The encyclopedia mentions different sources of purple dye, particularly the
murex snail, the highly prized source of
Tyrian purple, as well as the value and origin of the
pearl and the invention of
fish farming and
oyster farming. The keeping of
aquariums was a popular pastime of the rich, and Pliny provides anecdotes of the problems of owners becoming too closely attached to their fish. Birds are described next, starting with the
ostrich and the mythical
phoenix. Much detail is spent with eagles, which are "looked upon as the most noble", followed by the other birds of prey. Pliny classifies birds based on the structure of their feet, noting the connection between their shape and the diet/habitat associated with their owners. He praises the song of the
nightingale, and considers the connection between birdsong and omens.
Bats are listed among the other "winged animals" but are recognised as viviparous and nurse their young with milk. This is followed by an extensive overview of animal reproduction, senses, and feeding and resting behaviour. Finally, insects and other arthropods are listed. Pliny devotes considerable space to
bees, which he admires for their industry, organisation, and
honey, discussing the significance of the
queen bee and the use of smoke by
beekeepers at the hive to collect
honeycomb. As well, the
silkworm and silk production are described, the discovery of which is attributed to a woman named Pamphile (no reference is made to China). The coverage of zoology ends with an account of animal anatomy. Pliny correctly identifies the origin of
amber as the fossilised
resin of pine trees. Evidence cited includes the fact that some samples exhibit encapsulated insects, a feature readily explained by the presence of a viscous resin. He mentions how it exerts a charge when rubbed.
Botany Botany is handled in Books XII to XVIII, with Theophrastus as one of Pliny's sources. The manufacture of
papyrus and the various grades of papyrus available to Romans are described. Different types of trees and the properties of their wood are explained in Books XII to XIII. The vine, viticulture and varieties of grape are discussed in Book XIV, while Book XV covers the
olive tree in detail, followed by other trees including the apple and pear, fig, cherry,
myrtle and
laurel, among others. Pliny gives special attention to spices, such as
pepper,
ginger, and
cane sugar. He mentions different varieties of pepper, whose values are comparable with that of gold and silver, while sugar is noted only for its medicinal value. He is critical of
perfumes: "Perfumes are the most pointless of luxuries, for pearls and jewels are at least passed on to one's heirs, and clothes last for a time, but perfumes lose their fragrance and perish as soon as they are used." He gives a summary of their ingredients, such as
attar of roses, which he says is the most widely used base. Other substances added include
myrrh,
cinnamon, and
balsam gum.
Drugs, medicine and magic A major section of the
Natural History, Books XX to XXIX, discusses matters related to medicine, especially plants that yield useful drugs. Pliny lists over 900 drugs, compared to 600 in
Dioscorides's , 550 in Theophrastus, and 650 in
Galen. The poppy and
opium are mentioned; Pliny notes that opium induces sleep and can be fatal. Diseases and their treatment are covered in book XXVI. Pliny addresses
magic in Book XXX. He is critical of the Magi, attacking
astrology, and suggesting that magic originated in medicine, creeping in by pretending to offer health. He names
Zoroaster of
Ancient Persia as the source of magical ideas. He states that
Pythagoras,
Empedocles,
Democritus and
Plato all travelled abroad to learn magic, remarking that it was surprising anyone accepted the doctrines they brought back, and that medicine (of Hippocrates) and magic (of Democritus) should have flourished simultaneously at the time of the
Peloponnesian War.
Agriculture harvesting machine The methods used to cultivate crops are described in Book XVIII. He praises
Cato the Elder and his work
De Agri Cultura, which he uses as a primary source. Pliny's work includes discussion of all known cultivated crops and vegetables, as well as herbs and remedies derived from them. He describes machines used in cultivation and processing the crops. For example, he describes a simple mechanical
reaper that cut the ears of wheat and
barley without the straw and was pushed by oxen (Book XVIII, chapter 72). It is depicted on a
bas-relief found at
Trier from the later Roman period. He also describes how grain is ground using a pestle, a hand-mill, or a mill driven by
water wheels, as found in
Roman water mills across the Empire.
Metallurgy Pliny extensively discusses metals starting with gold and silver (Book XXXIII), and then the base metals copper,
mercury, lead,
tin and iron, as well as their many alloys such as
electrum,
bronze,
pewter, and steel (Book XXXIV). He is critical of greed for gold, such as the absurdity of using the metal for coins in the early Republic. He gives examples of the way rulers proclaimed their prowess by exhibiting gold looted from their campaigns, such as that by Claudius after conquering Britain, and tells the stories of
Midas and
Croesus. He discusses why gold is unique in its
malleability and
ductility, far greater than any other metal. The examples given are its ability to be beaten into fine
foil with just one ounce producing 750 leaves four inches square. Fine gold
wire can be woven into cloth, although imperial clothes usually combined it with natural fibres like wool. He once saw
Agrippina the Younger, wife of Claudius, at a public show on the
Fucine Lake involving a naval battle, wearing a military cloak made of gold. He rejects Herodotus's claims of
Indian gold obtained by ants or dug up by
griffins in
Scythia.
Silver, he writes, does not occur in native form and has to be mined, usually occurring with lead ores. Spain produced the most silver in his time, many of the mines having been started by
Hannibal. One of the largest had galleries running up to two miles into the mountain, while men worked day and night draining the mine in shifts. Pliny is probably referring to the
reverse overshot water-wheels operated by treadmill and found in Roman mines. Britain, he says, is very rich in lead, which is found on the surface at many places, and thus very easy to extract; production was so high that a law was passed attempting to restrict mining. Fraud and forgery are described in detail; in particular
coin counterfeiting by mixing copper with silver, or even admixture with iron. Tests had been developed for counterfeit coins and proved very popular with the victims, mostly ordinary people. He deals with the liquid metal mercury, also found in
silver mines. He records that it is toxic, and
amalgamates with gold, so is used for refining and extracting that metal. He says mercury is used for
gilding copper, while
antimony is found in silver mines and is used as an
eyebrow cosmetic. The main ore of mercury is
cinnabar, long used as a pigment by painters. He says that the colour is similar to
scolecium, probably the
kermes insect. The dust is very toxic, so workers handling the material wear face masks of bladder skin. Copper and bronze are, says Pliny, most famous for their use in statues including colossi, gigantic statues as tall as towers, the most famous being the
Colossus of Rhodes. He personally saw the massive statue of
Nero in Rome, which was removed after the emperor's death. The face of the statue was modified shortly after Nero's death during Vespasian's reign, to make it a statue of
Sol.
Hadrian moved it, with the help of the architect Decrianus and 24 elephants, to a position next to the
Flavian Amphitheatre (now called the
Colosseum). Pliny gives a special place to iron, distinguishing the hardness of steel from what is now called
wrought iron, a softer grade. He is scathing about the use of iron in warfare.
Mineralogy intaglio (1st century AD) depicting
Nero as
Apollo playing the lyre
(Cabinet des Médailles) In the last two books of the work (Books XXXVI and XXXVII), Pliny describes many different
minerals and
gemstones, building on works by Theophrastus and other authors. The topic concentrates on the most valuable gemstones, and he criticises the obsession with luxury products such as
engraved gems and
hardstone carvings. He provides a thorough discussion of the properties of
fluorspar, noting that it is carved into vases and other decorative objects. The account of magnetism includes the myth of
Magnes the shepherd. Pliny moves into
crystallography and
mineralogy, describing the
octahedral shape of the diamond and recording that diamond dust is used by gem engravers to cut and polish other gems, owing to its great
hardness. He states that
rock crystal is valuable for its transparency and hardness, and can be carved into vessels and implements. He relates the story of a woman who owned a ladle made of the mineral, paying the sum of 150,000
sesterces for the item. Nero deliberately broke two crystal cups when he realised that he was about to be deposed, so denying their use to anyone else. Pliny returns to the problem of fraud and the detection of false gems using several tests, including the scratch test, where counterfeit gems can be marked by a steel file, and genuine ones not. He refers to using one hard mineral to scratch another, presaging the
Mohs hardness scale. Diamond sits at the top of the series because, Pliny says, it will scratch all other minerals.
Art history Pliny's chapters on
Roman and
Greek art are especially valuable because his work is virtually the only available classical source of information on the subject. In several passages, he gives proof of independent observation (XXXIV:38, 46, 63, XXXV:17, 20, 116 seq.). He prefers the marble
Laocoön and His Sons in the palace of Titus (widely believed to be the statue that is now in the
Vatican) to all the pictures and bronzes in the world (XXXVI:37). The statue is attributed by Pliny to three sculptors from the island of Rhodes:
Agesander, Athenodoros (possibly son of Agesander) and Polydorus. In the temple near the
Flaminian Circus, Pliny admires the
Ares and the
Aphrodite of
Scopas, "which would suffice to give renown to any other spot". He adds: At Rome indeed the works of art are legion; besides, one effaces another from the memory and, however beautiful they may be, we are distracted by the overpowering claims of duty and business; for to admire art we need leisure and profound stillness (XXXVI:27).
Mining , the most important gold mine in the Roman Empire, resulted from the mining technique. Pliny provides lucid descriptions of
Roman mining. He describes
gold mining in detail, with large-scale use of water to scour alluvial gold deposits. The description probably refers to mining in Northern Spain, especially at the large
Las Médulas site. Pliny describes methods of underground mining, including the use of
fire-setting to attack the gold-bearing rock and so extract the ore. In another part of his work, Pliny describes the use of
undermining to gain access to the veins. Pliny was scathing about the search for precious metals and gemstones: "Gangadia or
quartzite is considered the hardest of all things – except for the greed for gold, which is even more stubborn." Book XXXIV covers the base metals, their uses and their extraction. Copper mining is mentioned, using a variety of ores including
copper pyrites and
marcasite, some of the mining being underground, some on the surface. Iron mining is covered, followed by lead and tin. ==Reception==