fishes. They consisted chiefly of the teeth, scales and fins,
even the bones being perfectly preserved in comparatively few
instances. He therefore adopted his well-known classification,
which divided fishes into four groups--viz. Ganoids,
Placoids, Cycloids and Ctenoids, based on the nature of
the scales and other dermal appendages. While Agassiz
did much to place the subject on a scientific basis, his
classification has not been found to meet the requirements
of modern research. As remarked by Dr A. Smith Woodward,
he sought to interpret the past structures by too rigorous
a comparison with those of living forms. (See Catalogue
of Fossil Fishes in the British Natural History Museum.)
As the important descriptive work of Agassiz proceeded, it
became obvious that it would over-tax his resources, unless
assistance could be afforded. The British Association came
to his aid, and the earl of Ellesmere--then Lord Francis
Egerton--gave him yet more efficient help. The original
drawings made for the work, chiefly by Dinkel, amounted
to 1290 in number. These were purchased by the Earl, and
presented by him to the Geological Society of London.
In 1836 the Wollaston medal was awarded by the council of
that society to Agassiz for his work on fossil ichthyology;
and in 1838 he was elected a foreign member of the Royal
Society. Meanwhile the invertebrate animals engaged his
attention. In 1837 he issued the ``Prodrome'' of a monograph
on the recent and fossil Echinodermata, the first part of which
appeared in 1838; in 1839-1840 he published two quarto volumes
on the fossil Echinoderms of Switzerland; and in 1840-1845 he
issued his Etudes critiques sur les mollusques fossiles.
Subsequently to his first visit to England in 1834, the labours
of Hugh Miller and other geologists brought to light the
remarkable fishes of the Old Red Sandstone of the north-east of
Scotland. The strange forms of the Pterichthys, the
Coccosteus and other genera were then made known to geologists
for the first time. They naturally were of intense interest
to Agassiz, and formed the subject of a special monograph
by him published in 1844-1845: Monographie des poissons
fossiles du Vieux Gres Rouge, ou Systeme Devonien
(Old Red Sandstone) des Iles Britanniques et de Russie.
The year 1836 witnessed the inauguration of a new investigation,
which proved to be of the utmost importance to geological
science. Previously to this date de Saussure, Venetz,
Charpentier and others had made the glaciers of the Alps
the subjects of special study, and Charpentier had even
arrived at the conclusion that the erratic blocks of alpine
rocks scattered over the slopes and summits of the Jura
mountains had been conveyed thither by glaciers. The question
having attracted the attention of Agassiz, he not only made
successive journeys to the alpine regions in company with
Charpentier, but he had a hut constructed upon one of the Aar
glaciers, which for a time he made his home, in order to
investigate thoroughly the structure and movements of the
ice. These labours resulted in the publication of his grand
work in two volumes entitled Etudes sur les glaciers,
1840. Therein he discussed the movements of the glaciers,
their moraines, their influence in grooving and rounding
the rocks over which they travelled, and in producing the
striations and roches moutonnees with which we are now so
familiar. He not only accepted Charpentier's idea that some
of the alpine glaciers had extended across the wide plains and
valleys drained by the Aar and the Rhone, and thus landed parts
of their remains upon the uplands of the Jura, but he went still
farther. He concluded that, at a period geologically recent,
Switzerland had been another Greenland; that instead of a few
glaciers stretching across the areas referred to, one vast
sheet of ice, originating in the higher Alps, had extended
over the entire valley of north-western Switzerland until
it reached the southern slopes of the Jura, which, though
they checked and deflected its further extension, did not
prevent the ice from reaching in many places the summit of the
range. The publication of this work gave a fresh impetus
to the study of glacial phenomena in all parts of the world.
Thus familiarized with the phenomena attendant on the
movements of recent glaciers, Agassiz was prepared for a
discovery which he made in 1840, in conjunction with William
Buckland. These two savants visited the mountains of Scotland
together, and found in different localities clear evidence of
ancient glacial action. The discovery was announced to the
Geological Society of London in successive communications from
the two distinguished observers. The mountainous districts
of England and Wales and Ireland were also considered to
constitute centres for the dispersion of glacial debris; and
Agassiz remarked ``that great sheets of ice, resembling those
now existing in Greenland, once covered all the countries
in which unstratified gravel (boulder drift) is found;
that this gravel was in general produced by the trituration
of the sheets of ice upon the subjacent surface, &c.''
In 1842-1846 he issued his Nomenclator Zoologicus, a
classified list, with references, of all names employed in
zoology for genera and groups--a work of great labour and
research. With the aid of a grant of money from the king of
Prussia, Agassiz, in the autumn of 1846, crossed the Atlantic,
with the twofold design of investigating the natural history
and geology of the United States and delivering a course of
lectures on zoology, by invitation from J. A. Lowell, at the
Lowell Institute at Boston; the tempting advantages, pecuniary
and scientific, presented to him in the New World induced
him to settle in the United States, where he remained to the
end of his life. He was appointed professor of zoology and
geology in Harvard University, Cambridge, U.S., in 1847.
In 1852 he accepted a medical professorship of comparative
anatomy at Charlestown, but this he resigned in two years.
The transfer to a new field and the association with
fresh objects of interest gave his energies an increased
stimulus. Volume after volume now proceeded from his pen:
some of his writings were popular, but most of them dealt
with the higher departments of scientific research. His work
on Lake Superior, and his four volumes of Contributions to
the Natural History of the United States, 1857-1862, were
of this latter character. We must not overlook the valuable
service he rendered to science by the formation, for his own
use, of a catalogue of scientific memoirs--an extraordinary
work for a man whose hands were already so full. This
catalogue, edited and materially enlarged by the late Hugh
E. Strickland, was published by the Ray Society under the
title of Bibliographia Zoologiae et Geologiae, in 4 vols.,
1848-1854. Nor must we forget that he was building up another
magnificent monument of his industry in the Museum of Natural
History, which rose under his fostering care, at Cambridge.
But at length the great strain on his physical powers began to
tell. His early labours among the fishes of Brazil had often
caused him to cast a longing glance towards that country,
and he now resolved to combine the pursuit of health with the
gratification of his long cherished desires. In April 1865
he started for Brazil, with his wife and class of qualified
assistants. An interesting account of this expedition,
entitled A Journey in Brazil (1868), was published by Mrs
Agassiz and himself after they returned home in August 1866.
In 1871 he made a second excursion, visiting the southern shores
of the North American continent, both on its Atlantic and its
Pacific sea-boards. He had for many years yearned after the
establishment of a permanent school where zoological science
could be pursued amidst the haunts of the living subjects of
study. The last, and possibly the most influential, of
the labours of his life was the establishment of such an
institution, which he was enabled to effect through the
liberality of Mr John Anderson, a citizen of New York. That
gentleman, in 1873, not only handed over to Agassiz the island
of Penikese, in Buzzard's Bay, on the east coast, but also
presented him with $50,000 wherewith permanently to endow it
as a practical school of natural science, especially devoted
to the study of marine zoology. Unfortunately he did not
long survive the establishment of this institution. The
disease with which he had struggled for some years proved
fatal on the 14th of December 1873. He was buried at Mount
Auburn. His monument is a boulder selected from the moraine
of the glacier of the Aar near the site of the old Hotel des
Neuchatelois, not far from the spot where his hut once stood;
and the pine-trees which shelter his grave were sent from his
old home in Switzerland. His extensive knowledge of natural
history makes it somewhat remarkable to find that from first
to last he steadily rejected the doctrine of evolution, and
affirmed his belief in independent creations. When studying
the superficial deposits of the Brazilian plains in 1865,
his vivid imagination covered even that wide tropical area,
as it had covered Switzerland before, with one vast glacier,
extending from the Andes to the sea. This view, however,
has not been generally accepted. His daring conceptions were
only equalled by the unwearied industry and genuine enthusiasm
with which he worked them out; and if in details his labours
were somewhat defective, it was only because he had ventured
to attempt what was too much for any one man to accomplish.
It may be interesting to mention that the charming verses
written by Longfellow on ``The fiftieth birthday of
Agassiz'' were read by the author at a dinner given to
Agassiz by the Saturday Club in Cambridge, Mass., in 1857.
Louis Agassiz was twice married, and by his first wife he had
an only son, Alexander Agassiz (q.v.), born in 1835; in 1850,
after her death, he married his second wife, Elizabeth Cabot
Cary of Boston, Mass., afterwards well known as a writer and
as an active promoter of educational work in connexion with
Radcliffe College (see an article on Radcliffe College, by
Helen Leah Reed in the New England Magazine for January 1895).
AUTHORITIES--L. Agassiz, His Life and Correspondence, 2 vols.,
by E. C (Mrs) Agassiz (London, 1885); Louis Agassiz, His Life and
Work, by C. F. Holder (New York and London, 1893). (H. B. Wo.)
AGATE, a term applied not to a distinct mineral species,
but to an aggregate of various forms of silica, chiefly
Chalcedony (q.v..) According to Theophrastus the agate
(achates) was named from the river Achates, now the Drillo,
in Sicily, where the stone was originally found. Most agates
occur as nodules in eruptive rocks, or ancient lavas, where
they represent cavities originally produced by the disengagement
of vapour in the molten mass, and since filled, wholly or
partially, by siliceous matter deposited in regular layers
upon the walls. Such agates, when cut transversely, exhibit
a succession of parallel lines, often of extreme tenuity,
giving a banded appearance to the section, whence such stones
are known as banded agate, riband agate and striped agate.
Certain agates also occur, to a limited extent, in veins, of
which a notable example is the beautiful brecciated agate of
Schlottwitz, near Wesenstein in Saxony--a stone mostly composed
of angular fragments of agate cemented with amethystine quartz.
In the formation of an ordinary agate, it is probable that
waters containing silica in solution--derived, perhaps,
