France now supplies her own market and exports 300,000 ounces of silkworm eggs annually. In worms affected with flacherie the food ferments in the alimentary tract and sustains vibrios and certain fungi. This disease is probably induced by improper care of the eggs. Gattine is probably only a modification of flacherie. The cause of grasserie (q.v.) is unknown. It is the least fatal of silkworm diseases. To keep silkworms healthy they must be reared in a suitable and constant temperature. Humidity, ventilation, and cleanliness must also be strictly and constantly attended to. Lime is used for whitewashing the walls and buildings in which the worms are reared, and sulphur fumes for sterilizing the trays.

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CULTURE OF SILKWORMS. The leaf of the white mulberry (Morus alba) is apparently the natural food of the domestic silkworm. There are many horticultural varieties of this plant, some much better adapted than others to commercial silk culture, and some better suited to certain localities. The Morus moretti, the Morus multicaulis, and the black mulberry (Morus nigra) are also used. The red mulberry (Morus rubra) does not make good food, and the paper mulberry (Broussonetia papyrifera) is also valueless. The best varieties of mulberries are propagated by means of seeds and by cuttings. The trees should be planted well apart and should be pruned so as to form a short trunk and a close low head. Silkworm eggs are kept through the winter at low temperature, the embryo beginning to take form when the temperature rises above 50° F. The receptacle in which they are stored should be ventilated, the air should not be moist, and great care should be taken to keep them out of the reach of mice and insects. The eggs are hatched in an artificial incubator or by natural heat. When an incubator is used the temperature should be gradually increased until 73° F. is reached. The whitening of the eggs denotes the near approach of the hatching. The eggs should then be covered with sheets of tulle or finely perforated paper, sprinkled over with finely cut white mulberry leaves. The young caterpillars will at once mount to the leaves, and should be fed eight to ten times during twenty-four hours. After each feeding the lower sheet of perforated paper or tulle should be removed with the frass. About the sixth day they will begin to molt and pass into the second stage. As the worms increase in size, paper in which the perforations are larger should be used, and the same general directions followed for each stage until the fifth has been reached.

The worms have now grown to nearly full size, and are very voracious, and it is very difficult to satisfy their appetite. After five days in the fifth stage they are ready to spin. In making preparations for spinning, dry brush, bundles of straw or shavings or finely split-up wood may be used. The brush or straw should be placed upright between the feeding shelves, in rows, about 16 inches apart, the tops spread out to form arches and to allow the worms plenty of room to spin. The temperature during spinning should be 75° F., and the humidity throughout the rearing about 65°. The rearing-room should be well ventilated, and before introducing the worms should be disinfected with chloride

of lime or sulphur. One ounce of eggs contains approximately 40,000, and the space required may be estimated by allowing one square yard for this amount at birth, on the fourth day two square yards, for the second stage four square yards, three days later eight square yards, for the third stage 16 square yards, for the fourth stage 32 square yards, and for the fifth stage 60 square yards. Plenty of space is desirable, since when crowded the worms will not be so robust. A mean temperature of about 74° F. is the best. There are many commercial varieties of the silkworm graded асcording to the size, color, and quality of the cocoon. When the cocoons are completed, which is known by the absence of any sound within, they are carefully sorted, and a certain number are kept for laying. The sexes are readily known by the difference of shape as well as of size, the female being plumper and the male, besides being much smaller, having a central depression and sharper extremities. The French growers sort them into nine varieties, those which are less compact, or in which the worm has died-a fact known by external indications -being separated from the good ones. When the sorting is finished, the cocoons are placed in an oven with a gentle heat, which kills the inclosed chrysalis, otherwise they would all become perforated by the insect eating through. The cocoons are then ready for the first stage in the manufacturing process, which consists in the removal and winding of the fibrous covering as described under SILK.

OTHER SILKWORMS. It is supposed by some entomologists that the original wild silkworm from which descended the silkworm of commerce is a species known as Theophila Huttoni, which occurs in Japan, the Northwest Himalayas, and Assam. The moth is of the same size as that of Bombyx mori, is light brown in color, and has the characteristic markings on the wings. The larva almost precisely resembles the domestic silkworm, but has a pair of small black thorns on the back of each segment of the abdomen. It seems very unlikely, however, that this species could have been the ancestor of Bombyx mori, since it lacks palpi, which are present in the Bombyx.

Oriental people have utilized the cocoons of a number of species of bombycid moths in the manufacture of silk goods. The so-called tussah, tusseh, or tusser silkworm is Antheræa mylitta, a species which occurs in China, India, and Ceylon. In Upper India this silk is extensively produced, and the cocoons are collected in the jungle districts by the Sahars and other halfwild castes who live in such places. Other silkworms which are said to be used in the manufacture of tusseh silk are Antheræa pernyi, from China; Antheræa Assama (Saturnia Perottetti and Antheræa mezankooria are synonyms of this species), a native of Assam, and there called 'moonga' or 'moogha;' Antheræa Roylei, from India; Antherœa Helferi from Sikhim; Antheræa jana, from Java; Antheræa Frithii, from Sikhim, Bhutan, and Darjeeling; and Antheræa larissa, from Java. The very large and beautiful Attacus atlas, from India, Ceylon, Burma, and Java, is also said to produce cocoons used in making tusseh silk.

The wild silkworms which have received the

The yama-mai silkworm is commonly raised in Japan and its cocoon is large, heavy, and handsome, and of a yellowish-green color. It is readily reeled, and its silk ranks commercially next to that of the domestic silkworm. The silk is strong and valuable. It bleaches well and may then be dyed. Fewer threads are required to make a strand than with Bombyx mori, and the cocoons unwind with perfect ease by the ordinary process. The life of the worm lasts from 50 to 80 days, and it feeds on all kinds of oak, but prefers those of the white oak group.

The pernyi silkworm has been cultivated in Europe with better success than the yamamai. It develops more rapidly, is double-brooded, and passes the winter in the chrysalis state. The cocoon is not so valuable, though ranking probably third best among the different silkworm

cocoons.

The ailanthus silkworm is utilized extensively in North China. It has been known in Europe since the middle of the last century, and has been cultivated there as well as in the United States with perfect success. The cocoons, however, cannot be reeled successfully, and their silk is utilized principally by carding processes.

In the United States several species of silkworm moths occur, and their caterpillars spin an abundance of silk of a strong and durable quality. The 'American' silkworm (Telea Polyphemus) is a large moth of a buff color, whose caterpillar feeds upon the leaves of many trees, including oak, willow, hickory, maple, apple, sycamore, and many others. The cocoon is formed of strong silk, which when unwound has a glossy fibre. It is oval and closed at both ends, dense, and generally fastened to a leaf or leaves with which it sometimes falls to the ground. The fibres are intermixed and cemented with a gummy substance which when dry gives the cocoon a chalky appearance. The principal difficulty in reeling the cocoon is in the hard matter which binds the threads. This, however, may be softened, and no doubt the cocoon could be improved by a process of continued selection. The insect has one generation each year in the Northern States and two in the Southern States, and passes the winter in the chrysalis state.

The large luna moth (Tropœa luna) is a beautiful species of a delicate green color, with long tails to the hind wings, whose larva feeds on several forest trees and whose cocoon is less dense than that of the polyphemus moth. The cocoons of these two species have the same general characteristics as those of the yamamai silkworm. Another native North American silkworm (Callosamia promethia) resembles in many respects the ailanthus worm. Its cocoon, like that species, is open and is in the same way difficult to reel. It feeds on ash, sassafras, wild cherry, maple, lilac, birch, and other trees. The largest

VOL. XVIII.-12.

of the American silkworms is the larva of Samia cecropia, a beautiful moth of a grayish brown color marked with reddish and yellowish spots and bands. The large green larva, which bears six coral-red tubercles on its thorax and smaller blue tubercles on its abdomen, feeds upon the apple and other rosaceous plants, as well as upon hazel, hickory, maple, willow, and honey-locust. The cocoon is peculiar in being apparently double. There is a thick, wrinkled outer layer which resembles strong brown paper and which covers an inner oval cocoon composed of the same kind of silk, but closely woven like that of the mulberry silkworm. Nearly related to this species are Samia Gloveri, of the Rocky Mountain region; Samia columba, of the North Atlantic States; and Samia rubra, from the Pacific States. In Mexico there are several large silkworm moths of the Saturnian group which produce quantities of silk, but it has not been commercially utilized or experimented with. There is another group of moths belonging to the family Psychidæ, in which the larva makes a large bag of silk which it carries about with it to protect its soft body from the attacks of birds. A common American example is the bagworm (q.v.) or basket-worm. This silk has not been utilized except in China. BIBLIOGRAPHY. Consult: Riley, Fourth Annual Report State Entomologist of Missouri (Jefferson City, 1872); Riley, "The Mulberry Silkworm," in Bulletin No. 9, Division of Entomology, United States Department of Agriculture (Washington, 1886); Kelly, "The Culture of the Mulberry Silkworm," in Bulletin No. 39 (ib., 1903); Villon, La Soie (Paris, 1890); Verson and Quajat, Il filugello e l'arte sericola (Padova,

1896). See SILK.

SILKWORM GUT. A material used by anglers to form the hook end of a fish-line. Its advantages are its extreme tenacity and its transparency or invisibility in water. It is prepared from the viscid secretion to be found in the silkworm (q.v.) just before it is ready to begin to spin. The grub is immersed in strong vinegar for several hours and the substance which, if it had lived, would have been spun into a cocoon, is forcibly drawn out from the dead worm. This thread is first soaked in cold water and then in a caustic solution. This loosens the outer covering, which is next removed. The silk is then dried in shady place. If simply dried it will be of a yellowish hue; the pure white thread is produced by bleaching in sulphur fumes. The manufacture of gut strings is carried on in Italy and Greece, and other silk-growing countries, but particularly in Spain, the principal market being Valencia. It takes from 20,000 to 30,000 threads to make a pound, the first price for a pound being from $25 to $30.

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SILL, EDWARD ROWLAND (1841-87). An American poet and essayist, born at Windsor, Conn. He graduated at Yale in 1861, resided till 1866 on the Pacific Coast, studied theology at Harvard, and after several years of teaching and literary work in the East was made principal of the Oakland, Cal., High School (1871) and in 1874 professor of English in the University of California. He returned to the East in 1882. He wrote: Hermione, and Other Poems; The Hermitage, and Other Poems (1867); The Venus of Milo, and Other Poems (1882). A posthumous selection embracing most of his better verse appeared in 1888. Two years later was published a posthumous collection of prose, "Being Essays in Literature and Education, and Friendly Letters." The small poetic production of Sill, who was a man of rare temperament and insight, is notable for carefulness of diction, delicacy of feeling, and a dominating strain of spiritual optimism. His thoughtful work has steadily grown in influence and seems likely to maintain a modest place in American literature.

reminiscences of his distinguished contemporaries are given in these volumes. During his long career Silliman was an active participant in all the affairs of Yale College-the organization of the Medical School, the formation of a cabinet of minerals, the acquisition of Colonel Trumbull's paintings, and the purchase of the Clark telescope.

His son, BENJAMIN, JR. (1816-85), was also a chemist, and was born in New Haven, Conn. He graduated at Yale College in 1837, becoming an assistant to his father, and in 1842 fitted up, in one of the college buildings, chemical labora

duty at the Watervliet Arsenal. From 1854 to 1857 he was assistant professor of geography and history at West Point, and then was again on duty in the Ordnance Department until January, 1861, when he resigned from the army and became professor of mathematics in the Brooklyn Polytechnic Institute. In April, however, he was appointed by the Governor of Ohio assistant adjutant-general of that State. He became colonel of the Thirty-third Ohio Volunteers in August, 1861, and commanded his regiment in the campaigns in Kentucky, Tennessee, and Alabama during the next year. He commanded a brigade in the movement against Nashville in February, 1862, and the subsequent operations in northern Alabama, and at Huntsville. On July 16, 1862, he was commissioned brigadier-general of volunteers, and commanded a division at the battle of Perryville, and in the pursuit of General Bragg's army. He was killed in the battle of Stone River, December 31, 1862.

SIL'LIMAN, BENJAMIN (1779-1864). An American scientist, born at North Stratford (now Trumbull), Conn., the son of Gold Selleck Silliman, a general in the army of the Revolution. After graduating at Yale in 1796 he studied law, became a tutor in Yale, was soon chosen to be a professor of natural science, and went abroad to fit himself for the chair in which he became teacher of chemistry, mineralogy, geology, and pharmacy. He held his professorship in Yale from 1802 to 1864-from 1853 onward as professor emeritus. He was honored and beloved as a teacher, and acquired even greater distinction as a lecturer, especially on geology. These courses began at New Haven in

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1831, and were so much appreciated that Silli

man was selected to give twenty-four lectures before the Lowell Institute of Boston, in its first session (1839-40). In 1818 he established the American Journal of Science (often quoted as 'Silliman's Journal'), which has been continued under successive members of his family to this day, and is still a leading American repository of scientific papers and intelligence. With Dr. Robert Hare he constructed the compound blow pipe. He published after his return from England a narrative of his journey, and fifty years later, at the end of a second journey, he pub lished a similar memoir. His Tour to Quebec (1819) was likewise widely read. His contributions to science were not numerous, one of those most famous at the time being an account (with J. L. Kingsley) of a remarkable meteor which fell at Weston in 1807. His Life was written by Professor George P. Fisher and published in two volumes (New York, 1868). Many entertaining

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of the Yale (now Sheffield) Scientific School. He was professor of medical chemistry and toxicology in the University of Louisville, Ky., from 1849 to 1854. In 1854 he succeeded his father

in the chair of chemistry, which he retained until 1870, continuing, however, to lecture in the medical department until his death. He gave popular lectures on scientific topics throughout the country, and was one of the editors of the American Journal of Science. He was the author of First Principles of Chemistry (1846; 2d ed. 1856); Principles of Physics (1858; ed. e. 1868); and American Contributions to Chemis

try (1875).

SILLIMANITE (named in honor of Benjamin Silliman). A mineral aluminum silicate that has a vitreous lustre, and is brown to green in color. It occurs in gneiss, mica schist, and other crystalline rocks, and is found in many localities in Bohemia, Bavaria, Saxony, and France, and in the United States in Massachusetets, Connecticut. New York, Delaware, and North Carolina. The fibrous varieties are commonly called fibrolite, while the name sillimanite is given to those varieties that are found in the form of long slender crystals.

SILO. An air-tight storage room either above ground or below, in which green crops usually cut small are tightly packed for future use. SILAGE.

See

SILO'AM (Heb. Shiloah, Shelah). A pool situated at the southern end of the eastern hill of Jerusalem, mentioned in Nehemiah iii. 15 and John ix. 7. Isaiah (viii. 6) speaks of the "waters of Shiloah that go softly." The water in this pool is supplied by the Virgin's Spring and is brought to the pool at the entrance to the Tyropœon valley by a tunnel over 1700 feet in length. The tunnel is rather winding, and about 25 feet from the Siloan end an important inscription was found in the wall in 1880. As translated by Driver, it reads: "(Behold) the piercing through, and this was the manner of the piercing through. Whilst yet (the miners were lifting up) the pick each towards his fellow, and whilst yet there were three cubits to be (cut through, there was heard) the voice of each calling to his fellow, for there was a fissure in the rock on the right hand. And on the day of the piercing through the miners smote each so as to meet his fellow, pick against pick; and there flowed the water from the source to the pool 1200 cubits; and 100 cubits was the height of the rock over the head of the miners." Hence the cutting was evidently done simultaneously from both ends. In default of any date, there has been much controversy as to the age of the inscription. The