Science Sittings

New Zealand Tablet, Volume 27, Issue 21, 27 May 1909, Page 835

Science Sittings

BY 4 VOLT

About Bread. * Bread was first made without leaven, heavy and solid. Then yeast was discovered, and yeast-risen bread came into use throughout the civilised world. Finally baking powder was devised, the most healthful, economical,- and convenient of all leavening or lightening agents. Yeast is a living plant. Mixed with the dough it causes fermentation and destruction of a part of the flour, and this produces carbonic-acid gas. The bubbles of this gas become entangled in the dough, swelling it up and making it spongy. In this process, however, a part of the most nutritious elements of the flour (estimated at 10 per cent) is destroyed in producing the leavening gas; there is always danger of sour dough, and there is a delay of many hours for the sponge to rise. Perfect bread is that in which wheat- is transposed into an available food without loss of any of its valuable properties. Baking powder is now largely used in place of yeast to leaven bread. It does precisely the same work — that is, swells up the dough and makes it porous and spongy. But the process is not destructive; the baking powder by itself produces the leavening gas. No part of the flour is decomposed or destroyed. Moreover, there is no mixing or kneading with the hands, no setting of sponge overnight, as the loaf is mixed and ready for the oven at once. Bread thus made cannot sour, but will retain its moisture and freshness, and may be eaten while hot or fresh without distress even by persons of digestion. The ease with whiih baking powder bread is made, its cleanliness and healthfulness, have caused it to supersede yeast bread with many of the best pastry cooks. The Breeding -of Oysters. The care of the breeding oyster and the plans adopted by the owners of oyster-beds for catching the ' spat,' or young oysters, when they fall to the bottom, by placing movable tiles or frames for them to fix themselves to, form an important part of the craft of the oyster man. ,It is a difficult business, and is" variously carried out in England, France, Holland, and America. The young oysters, when they have fixed themselves, are carried on the movable tiles or frames from one region to another for the purpose of encouraging their growth and avoiding a variety of dangers to their life and health (sometimes from the Bay of Biscay to s the mouth of the Thames !). They are often, but not always — finally fed up in sea ponds or inlets, which are peculiar in containing an enormous number of those very minute microscopic plants, with beautifully shaped siliceotis shells, which are known as diatoms. These are so abundant in such ponds as to form a sort of powder or cloud near the bottom, and the oysters draw them, day and night, by their gill-currents into their mouths, digest them, and grow fine and fat. The district of Marennes ,on the West Coast of France, is celebrated for having sea-ponds or tanks in which a wonderful diatom of a bright blue color abounds; so abundant are they that the cloud produced by them in the pools is of a deep cobalt blue. When oysters" are placed in these tanks to fatten, their gills or beards become rich blue-green in color. They lose the color after ten days, when removed to ordinary tanks. These are the celebrated green oysters or ,' Marennes vertes 'of French restaurants. The coloring matter of the little diatoms — swallowed by the million and digested — is taken up by the blood of the oyster from its stomach, and is excreted by certain corpuscles on the surface of the gills, just as red madder is deposited in the .bones of a pig fed upon madder, and as the feathers of the canary take up the color of cayenne pepper when it js mixed with the canary's food. It used to be thought that the green color of the green oyster is due to. copper — and that opinion was supported by the curious fact that the blood of all oysters and other molluscs, and also of lobsters, scorpions, and king-crabs, does really contain a minute quantity of copper, just as our bloood contains iron.

It may nof cure the housemaid's knee, Gout or appendicitis; But ills and chills before it flee, Dyspepsia or bronchitis ; It is a fact, it will not act To polish furniture, But to polish off a cold or cough Take Woods' Great Peppermint Cure.