Aug. 7, 1885.] 



♦ KNOWLEDGE ♦ 



forward some experiments commenced many years ago 

 with thermometers having long cylindrical bulbs of 

 equal dimensions representing the body of a clothes- 

 wearer. These bulJiis are clothed with properly-fitted 

 jackets of the different materials ; all raised to a given 

 temperature in a hot chamber, then set to cool down in 

 a cold chamber,, and their rates of cooling observed and 

 recorded. 



With Rumford's arrangement, eider-down took second 

 place in total time of cooling. (Hare's fur, 1,315 sees. ; 

 eiderdown, 1,305; beaver's fur, 1,296; raw silk, 1,284; 

 sheep's wool, 1,118; cotton wool, 1,046; fine lint, 1,032.) 

 The spun and woven fabrics, as will be remembered, 

 yielded larger advantage to woollen material, and all 

 were much inferior to tlie raw material. 



Among the raw iiiati-riiils iiIkivc cuniiici-ati'd, uuly eider 

 down is practically used fm- cImI liin^' in ils im w state. It 

 thuB takes jiniclicatli/ tlic lir.^t plac.', undn- lUimford's 

 mode of testing it. liat tlii.s lucahud dues la.t do justice 

 to eider down, as it destroys its specially efficient attri- 

 bute. To make sixteen grains of eider down occupy the 

 same space as the sixteen grains of other material it 

 must have been cimsidcralily vainiiuMl — squeezed, into a 

 much smaller bulk than i( s|inntaii((.iisly occupies. Had 

 it been allowed to (iiTn|.y iis full lailk, it would have 

 imprisoned a nuuli larnii- i|uaiLiity df air, and conse- 

 quently have achieved a much greater resistance to the 

 passage of heat. 



I have no hesitation in affirming that, weight for 

 weight, eider down is the most effective heat retainer of 

 all the clothing materials at present known. Until lately 

 it has been but indifferently appreciated and little used 

 in this country, though well undoi-stood and largely 

 used long ago, in North Germany, and North Europe 

 generally. 



The eider duck is an Arctic sea bird that sometimes 

 wanders as far south as the Hebrides, the Orkneys, and 

 Newfoundland. It is about the size of the smaller 

 varieties of our common domestic duck, with a more 

 pointed goose-like bill, and flatter head. Its colour is 

 yellowish brown, with black stripes. Like other aquatic 

 birds, it is clad with an underdown composed of delicate 

 fibres as fine as hairs, but much stiffer, and more elastic. 

 This beautiful fibrous structure holds imprisoned an un- 

 broken envelope of air, which not only keeps the bird 

 perfectly, dry, but sensibly increases its buoj-aucy. 



Perhaps I should add that this attribution of buoyancy 

 to the aerial envelope of ducks is a lurLsy of my own, 

 like my denial of the oiling of dui'k'.s fuailu r.s t.. kci-p 

 them" dry; but if " G. A." (n- any .iilur ivadn- is 

 sceptical, let him test the specilh- L'r,i\ii\ ^ I' a |ihukrd 

 duck, or a dead duck in wetted fiathns l.'v |ila(in._^- n .ui 

 the water. The jduckrd durk ^\ill .Muk'; ll.r ^^^l(r,l 

 specimen may llnat, lait ilslui'jhi alni\i' ilir surfaci- i-i 

 the water will cnutra.st cui-i.iu-ly wiili tlial ul' ihr li\-in-- 

 swimmer. If t he i-cadrp has Mill any iv-idiial alT.vl idu I'm]- 



and then 



fingei 



Aft.a 



.sheep. In tli 



that should pertain ic I hr duck's (.|. .1 li iu^;- if fhc fcaihci's 

 nnd down were oiled. 



I have at the present moment a loving and faithful 

 duck that feeds from my hand, and follows me like 

 n, dog. This docility has enabled me to detect the pro- 

 bable origin of the feather-oiling fables. At times the 

 animal bites tlio region near the tail very savagely, and 







proceeds with furthci- ( uci-jn a- n ; Mil nu over 



of the back. I hav ,-.,,; i - . - .-.],]].■ 



ceeding, but fiiid n-i ir,.- , , i . n ( 



usually wetted vci-y jialji.! Ill \ \\i'l! \^. <!•■•■. l-'u 



vation supplies a very simple and uiii-omantic 



the proceeding. Ducks, like all other poultrj-, 



fested with fleas ; the duck's fleas prefer the non-im 



parts of the body, and hence congregate on the back. 



Instead of a squeezing out of oil a driving out of fleas 



follows the pinching which Paley describes. 



An Arctic marine bird which, like the eider duck, 

 feeds on marine mollusca, and is consequently exposed to 

 rough surf washing, requires an abundant sujijily of sur- 

 rounding air cushion, especially on the breast. This also 

 serves as warm clothing during the bitter winter, but 

 niu..st be rather burdensome in the hot Arctic summer 

 time. At this period it disposes of such oppresive 

 clothing by tearing it off and using it for nest making. 

 So valuable is this down that in Iceland the eider duck 

 is rigidly protected, anybody who kills one is liable to a 

 heavy penalty (30 dols. in nesting time). They are 

 similarly preserved in Norway. When at Vardo (lat. 

 70° 22") I had to obtain special permission to visit a 

 little verdant island N E of the town where the eider 

 ducks were sitting. An official duck protector was sent 

 with me. We found the ducks curiously tame. One 

 was lifted off her nest, the mat of down and eggs carried 

 some distance, deliberately examined and replaced ; the 

 duck returned and resumed her sitting at once. 



The bed of down was about fifteen inches square and 

 two inches thick ; about 450 cubic inches of dark grey 

 fluff, with very little admixture of foreign matter. The 

 eggs about the size of our domestic duck eggs, green, or 

 greenish-blue, with black spots. The nests are robbed of 

 their down two or three times, and the duck renews it, 

 finally with some assistance from the drake. If the 

 robbing is repeated oftener, the nest is deserted, and the 

 ducks find another home. Hence the ncc. -.-ity f^i- 

 stringent regulations in localities where tiny supily a 

 notable revenue, as at Vardo, where a little ciiinniuniiy 

 numbering about 1,200 are dependent on two harvest <, 

 one of codfish, the other eider-down, with a small supple- 

 mentary crop of a luscious three-lobed, scarlet berry, the 

 vwltebeer, which covered the duck's island with a rich 

 carpet of its trailing vine, and spotted it all over, when I 

 was there, with millions of white flowers. The scene 

 presented by such verdant and floral luxuriance on a 

 bright sunny midnight in July violently corrects the 

 commonly prevailing delusions concerning the climate of 

 "the Arctic region.s." 



THE NEEDLE AND THREAD PLANT. 



THE Agave Ameri-enna, or maguey of the Mexicans, is 

 known as tlie century plant among our coUeetions, 

 111,- l-.iii. 1- ninn I , i ii _■ uiven to it from the, erroneous idea 

 tluit it lilnonad , nrr in a, hundred j'cars, and " with such 



taiued a height of twenty -seveu feet, and ha\ in^^ 

 forty flowering bunches, each with four hundred blc 



