[ 175 ] 13'2 



are changed for those of the white species: and the same efifect takes 

 place when the order is reversed. In the first case, if permitted, they 

 will eat so ravenously, as to be deprived of the ability to digest their 

 food, and will burst; in the latter, a derangement of their functions, 

 and general debility takes place. From the facts detailed in page 44, 

 of the leaves of both species of the mulberry being indiscriminately 

 eaten, when mixed, and given to the worms, it might be supposed 

 that no injury would arise from a change of the leaves of the white to 

 those of the red species, but the following case, among others which 

 could be cited, shows that the experiment is not safe. " On one oc- 

 casion, a neighbor being deficient in white mulberry leaves, about the 

 time the worms were preparing to spin, gave them a quantity of the 

 black [red] mulberry leaves. The worms fed readily upon them, but 

 immediately sickened, and performed their task of winding very im- 

 perfectly."* It is possible, that, in this case, a partial cause of the 

 cfTect produced, may have been the quantity of the food given to the 

 worms. The change of nourishment, when rendered necessary, should 

 be gradual. The danger arises, as in the preceding case, from a sub- 

 stitution of one leaf for another, in the late stage of their existence: 

 for it has been already observed, that, before this time, silkworms can 

 be supported upon lettuce and other leaves, and that afterwards resort 

 can be had safely and beneficially to those of the mulberry. A recent 

 experiment shows that, until this critical epoch no injury will attend 

 a change of the foreign for the native leaf. Mr. Prince^ of Flushing, 

 Long Island, " fed some silkworms until they were half-grown, upon 

 the white mulberry, and then finished them upon the native species; 

 they grew so rapidly, that they commenced spinning in twenty-one 

 days, and pioduced excellent silk." 



VII. Diseases from 'peculiar constitution of the air. 



The injurious influence of certain states of the air upon the produc- 

 tion of fruits, has long been observed by farmers and horticulturists, 

 particularly in respect to grapes; and the same influence is often ex- 

 perienced by the cultivators of silkworms. Dandolo has noticed the 

 extremely unfavorable state of the atmosphere in Italy in the year 1814, 

 These peculiar states of the atmosphere in certain localities, not being 

 veferrible to its sensible qualities, renders it impossible to guard against 

 the injurious clTeets produced by them on silkworms.! 



When such a state of the atmosphere takes place, we must be the 

 more particular and attentive in guarding against the usual and known 

 causes of disease. 



• George A. Tuffts, Esq. cf Worcester county, Massachusetts: answer to the silk- 

 circular. 



t It is much to be regretted that science has not yet enabled us to ascertain the pre- 

 cise causes to wliich the bad air, in particidar places, is to be ascribed. The Eudio- 

 meter will give the constituent proportions of the air of a place; but repeated experi- 

 ments with it, on land and sea, in balloons, and steeples highly elevated, and in deep 

 caves, in an orchard in bloom, and in the chamber where a malignant fever prevails, 

 trive results so very nearly similar, that it is impossible to ascrilie the health of one 

 place, or the prevalence of an epidemic in another, to tlie greater or less abundance 

 of tiny pQi'lion of the airs which enter into the composition of the atmosphere. 



