888 



INCUBATION, ARTIFICIAL 



IMPREST. A paper printed in the report on the public accounts, gives nn 

 authoritative definition of this technical term, so unintelligible to many persons. Tito 

 word ( imprest ' is generally used in opposition to the term ' final payment.' A final 

 payment is a payment made in final discharge of an obligation of the government to 

 the public creditor ; as, for instance, the payment of a bill for stores supplied to the 

 government, or the payment of a salary to a government clerk. An ' imprest' moans 

 an advance of public money, to enable the person to whom it may bo made to carry on 

 some public service; and tho person to whom tho advance is made is called the 

 ' imprest accountant.' 



XXVCOIVXBUSTIBXiX! CZiOTH is a tissue of tho fibrous mineral called amianthus 

 or asbestos. Cotton and linen cloth may be best rendered incapable of burning with 

 flame by being imbued with a solution of sal-ammoniac or of alum. 



INCUBATION, ARTIFICIAL The Egyptians have from time immemorial 

 been accustomed to hatch oergs by artificial warmth, without the aid of hens, in pe- 

 culiar stoves, called Mammals. M. de Re'aumur published in Prance, about a century 

 ago, some ingenious observations upon this subject; but M. Bonnemain was the first 

 person who studied with due attention all the circumstances of artificial incubation, 

 and mounted the process successfully upon the commercial scale. So far back as 

 1777 he communicated to tho Academy of Sciences an interesting fact, which ho had 

 noticed, upon the mechanism employed by chicks to break their shells ; and for some 

 time prior to the French Revolution he furnished tho Parisian market with excellent 

 poultry at a period of the year when the farmers had ceased to supply it. His estab- 

 lishment was ruined at that disastrous era, and no other has ever since been constructed 

 or conducted with similar care. His apparatus derives peculiar interest from the fact 

 that it was founded upon the principle of the circulation of hot water, by the intestine 

 motions of its particles, in a returning series of connected pipes ; a subject afterwards 

 illustrated in the experimental researches of Count Rumford. It has of late years 

 been introduced as a novelty into this country, and applied to warm the apartments of 

 many public and private buildings, The following details will prove that the theory 

 and practice of hot- water circulation were as perfectly understood by M. Bonnemain 

 fifty years ago as they are at the present day. They were then publicly exhibited at 

 his residence in Paris, and were afterwards communicated to the world at largo in the 

 interesting article of the Encyclopedic Technologique, intitled Incubation Artificielle, 

 under the head of Regulateur de Temperature. 



The apparatus of M. Bonnemain consisted : 1, of a boiler and pipes for the circula- 

 tion of water; 2, of a regulator calculated to maintain an equable temperature; 3, 

 of a stove -apartment, heated constantly to the degree best fitted for incubation, which 

 he called the hatching pitch. He attached to one side a poussiniere or chick-room, for 

 cherishing the chickens during' a few days after incubation. 



The boiler is represented in vertical section and ground plan, in figs. 1207 and 1208. 

 It is composed of a double cylinder of copper or cast iron I, I, having a grate b (see 



1207 



1208 



plan), an ashpit at d (section). The water occupies tho shaded space c, c. h, g,g, c, e, 

 are five vertical flues for conducting tho burnt air and smoke, which first rise in tho 

 two exterior flues e, e, then descend in tho two adjoining flues g, g, and finally remount 

 through the passages i, i, in the central flue h. During this upward and downward 

 circulation, as shown by the arrows 'in the section, tho products of combustion are made 

 to impart nearly the whole of their heat to tho water by which they are surrounded. 

 At the commencement, some burning paper or wood shavings are inserted at tho orifico 



