100 THE POPULAR SCIENCE MONTHLY. 



good in pastry, and mixed with fowls' eggs they improve ome- 

 lets. 



The question whether fowls or ducks are the better investment 

 for the production of eggs has to some extent been settled experi- 

 mentally in Germany and France in favor of ducks. They laid 

 more eggs than the fowls, and, though they were rather small- 

 er, they proved to be decidedly superior in nutritive material. 

 It may be doubted whether as much attention is paid in Eng- 

 land to the production of eggs as the utility of the food demands, 

 and particularly by the poor, to whom their value is a consider- 

 ation. Efforts should be made to induce all persons conveniently 

 circumstanced to keep hens and ducks, and there is reason to 

 believe that ducks are more profitable than hens, having regard 

 to the number and size of the eggs laid by them. The solid mat- 

 ter and the oil in a duck's egg exceeds that of a hen's egg by as 

 much as one fourth. 



Eggs, their dietetic use apart, are of great utility in many 

 branches of industry. In some, as in confectionery, both the 

 whites and yolks are used, but usually the two find separate ap- 

 plications. The whites are employed in calico-printing, in pho- 

 tography, in gilding, in clarifying wines and liquors, and by the 

 bookbinder on the leather previous to lettering or tooling. 



An egg-oil is obtained in Russia in large quantities and of 

 various qualities ; the best so fine as to far excel olive-oil for 

 cooking purposes. The less pure and very yellow qualities are 

 chiefly used in the manufacture of the celebrated Kazan soap. 

 Both of these products were shown at the London International 

 Exhibition in 1862, and at subsequent exhibitions. Neither the 

 oil for cooking purposes nor the soap are sufficiently cheap for 

 general use ; they are consumed only by the wealthy classes as 

 luxuries ; the soap, being regarded chiefly in the light of a cos- 

 metic, is a much- valued addition to a Russian lady's toilet neces- 

 saries. The yolk is also used for medicinal purposes. It was 

 used in the middle ages for the painter's art, before the discovery 

 of oil-colors, as in the chapter-house at Westminster. 



Eggs, whether to be used in culinary or pharmaceutical prepa- 

 rations, should be fresh. To determine this they should be ex- 

 amined by the light of a lamp. Fresh eggs are easily known by 

 their transparency when held up to the light. By keeping they 

 become cloudy, and when decidedly stale a distinct, dark, cloud- 

 like appearance is discernible opposite some portion of the shell. 

 Another simple mode is by placing the egg against the closed 

 eyelid, and if the end of the egg is void it will feel warm, where- 

 as if the egg is new laid it continues cold. A way to tell bad eggs 

 is to put them in a pail of water, and, if good, they will lie on 

 their sides ; if bad, they will stand on their small ends, the large 



