Goldsmith's Natural history : with notes from all the popular treatises that have been issued since the time of Goldsmith ... / [edited] by Henry Innes, with a life of Oliver Goldsmith by George Moir Bussey.

Oliver Goldsmith

Date:: [18??]

Credit: Goldsmith's Natural history : with notes from all the popular treatises that have been issued since the time of Goldsmith ... / [edited] by Henry Innes, with a life of Oliver Goldsmith by George Moir Bussey. Source: Wellcome Collection.

795/860 page 419

$The insect never proceeds from the egg till nature has providea it ti siifhcieni Kwppl}', and till the budding leaves are furnished in siinicient abundance for its support When the leaves are put forth, the worms seem to feel the genia summons, and bursting from their little eggs, crawl upon the leaves, where they feed with a most voracious appetite. Tims they become larger by degrees; antf after some months’ feeding, they lay, upon every leaf, small bundles, or cones of silk, wliich appear like so many golden apples, painted on a fine green ground. Such is the method of breeding them in the east; and without doubt it is best for the worms, and least troublesome for the feeder of them. But it is otherwise in our colder European climates; the frequent changes of the weather, and the heavy dews of our evenings, render keepuig them all night exposed subject to so many inconveniences, as to admit of no remedy.’^ It is true, that by the assistance ol nets, they may be preserved from the insults of birds; but the severe cold whether, which often succeeds the first heats of summer, as well as the rain and high winds, will destroy them all; and, therefore, to breed them in Europe, they must be sheltered and protected from every external injury.f * Sn.K-woRU IN Knolano.—The growth of the silk-wonn has also been tried, but with no great success, in this country. Evelyn computed that one mulberry-tree would feed as many silk-worms annually as would pro- duce seven pounds of silk. “ Acconling to that estimate,” says Barham, “ the two thou- sand trees already planted in Chelsea Park (which take up one-third of it) will make ]4,000 lbs. weight of silk; to be commonly worth but twenty shillings a pound, those trees must make 14,000/. jier annum.” Dur- ing the last century, seme French refugees in the south of Ireland made considerable planta- tions of the mulberry, and had begun the cultivation of silk with every appearance of success; but since their removal the trees have been cut down. In the vicinity of Loudon, also, a considerable plantation of mulberry-trees were purchased by the British, Irish, and Colonial Silk Company in 1825; but we have not learned whether this com- pany have any active measures now in ojie- ration. The manufacture of silk was introduced into this country in 1718, at Derby, by Mr. John Lombe, who travelled into Italy to ob- tain the requisite information ; but so jealous were the Italians of ihis, that, according to some statements, which have obtained belief, he fell a victim to their revenge, having been poisoned at the early age of twenty-nine.— InSBCT AKCHirECTORK. f Effbcxs ok Cold on Inskcts.—It is remarkable the extreme of cold to which in- sects and their eggs will be subjected ere the vital principle is destroyed. Spallanzani ob- serves that—“ Intense cold does not destroy the eggs of insects. The year 1709, when Fahrenheit’s thermometer fell to 1°, is cele- brated for its riguui and its fatal effects on (ilants and animals. Who can believe, ex- claims Boerhuave, that the severity of this winter did not destroy the eggs of insects, -specially those exposed to its influence in the open &eldH,ou the naked earth, or on the branches of trees ? Yet, when the spring had tempered the air, these eggs produced us they usually did after the mildest winters. Since that period there have been winters more severe. In France, during December, 1788, the thermometer fell considerably lower, and in several other temperate Euroiiean climates. “ I have exposed eggs to a more rigorous trial than the winter of 1799. Those of several insects, and annong others the silk- worm, moth, and elm butterfly {vaneasu polychhroa f) were inclosed in a glass vessel and buried live hours in a mixture of ice and sal gem (rock salt); the thermometer fell 6° below zero. In the middle of the following spring, however, caterpillars came from all the eggs, and at the same time as from those that had suffered no cold. In the following year, 1 submitted them to an experiment still more hazardous. A mixture of ice and sal gem with the fuming spirit of nitre (nitrate of ammonia), reduced the thermometer 22° below zeto, that is 23° lower than the cold of 1709. They were not injured, as I had evi- dent proof by their being hatched. “ Combining all these facts, we conclude that cold is less noxious to germs and eggs, than to animalcula and insects. Germs in general can support 2° below zero ; whereas of animalcula some die at the freezing point, and some at about 20°. The eggs of many insects continue fertile after being subjected to a temperature of 22° below zero, while in- sects themselves die at 16° and 14°. This I have ascertained in the eggs of the silk- worm moth, and of the elm butterfly; and although there are caterpillars and chiysa- lides able to resist great cold, I have uni- formly found it to be in a less degree than what can be resisted by their eggs. What can be the cause of so great a diflerence ? Insects killed at 16° and 14° are so jiene- trated and frozen by the cold, that their mem- bers do not yield to the pressure of the finger, and seem perfect ice under the knife. This$