SCIENCE IN PRACTICE.

Taranaki Daily News, Volume LII, Issue 389, 14 May 1910, Page 10

SCIENCE IN PRACTICE.

DEEP VOICES. The work of orators and singers lias been found <by Mr. Marage, of Paris, to vary greatly with the pitch of the voice. The bass voice is at a great disadvantage, and in the same shall it requires 17 to 18 times as much work as the baritone or tenor voice to give the same impression. Powerful, deep-voiced men are more fatigued by the same oratorical performance than more delicate men with voices of higher pitch, or than women and children. ROLLER SKATING. A physician who has made a careful study of the effects of roller ska tin <* has shown that excessive indulgence in this sport frequently results in liat feet, defective development of the leg muscles and impairment of the carriage and gait of the body. Roller skating is especially injurious to growing children, whose muscles, bones and joints are still in process of development. The muscles used in walking, especially those of the feet, remain inactive in roller skating, iwihile other muscles are overworked. Hence the body becomes or less deformed, especially in the case of young girls, who fail to acquire their normal grace and beauty of form.

MAGNESIUM AS STIMULANT. Professor, 'Mayer thinks he has, in magnesium, a powerful stimulant. He took some jellyfish, put ,them in salt water, and added pulverside magnesium to the solution. "After a few days of this treatment," he says, "they revived and became active, when every evidences proved that they were dead." Now, the metals such as sodium, magnesium, and calcium, have no power of any kind, and are inert, and pass through the digestive channels unchanged. This can oe proved by giving them, and watching the secretions. The salts of these materials, however, have power. Let the discharge be passed into .water, then filtered and tested, they will be found to contain magnesium, calcium, sodium, and others. LEAF-CHEWING STIMULANT. The leaves of the kat plant are a common stimulant among the natives of Abyssinia and Arabia. Consul-General R. P. Skinner reports that they are chewed when any special or long-con-tinued effort is to be made and tneir effect is to produce an agreeable sleeplessness and stimulation —a kind of intoxication of long duration —with none of the disagreeable features of ordinary inebriety. They enable messengers and soldiers to go without food for a number of days. They sometimes produce a state of drunkenness, like the alcohol of Europeans, but over-indulgence is rare, the effects of abuse of the habit being a tendency of the body to dry, and emaciation of the visage, with a trembling of the limbs and other nervous troubles. 'ln fe»me placfes merchants chew the leaves two or three times a day, the habit Toeing fairly comparable to the use of tea in Europe. The plant is specially cultivated as dwarf shoots, shrubs, and small trees — the dwarf plants being not more than 10 inches tall, and yielding the most tender, popular, and high-priced leaves.

SNAPSHOT OF EYE. . Color photography has been made an important auxiliary to eye-examination, and an eminent Paris eye specialist is no'w employing it. daily in his work. The ordinary examination of the eye is very painful sometimes to the patient, who has to submit to a prolonged scrutiny with a strong illumination thrown on the eye. M. Monpillard has now described at the Photographic Society of France how an instantaneous photograph iu natural colors is taken of the eye ; the photograph itself being submitted to critical examination afterwards. The patient is placed in front of a special camera, and a powerful light is thrown on the eye from an electric arc lamp. A snapshot is taken, an autochrome plate being used for the purpose. This plate, as is well known, gives, on being manipulated in the usual way, a perfect rendering in natural colors of the object photographed. The pigment colors are faithfully recorded, and the photograph serves in every way for the specialist's examination, so that the patient has only to submit to a moment's discomfort.

DRIVING A NAIL. "It takes an apprentice a full year to learn that he does not know how to drive a nail," says an expert carpenter. "When once he has realised this, it is only a matter of a few minutes to learn how it should be done. The commonest mistake is the belief that a hard blow with the hammer is more effective than several little taps, and the learner is inclined to admire the man who drives a nail all the way in with ■but one (blow. This is where he is wrong; four or five blows are much better than one. The reason is that one hard blow invariably makes the nail rebound, ever so slightly it is true, but enough to make it hold less firmly than it would if driven in gradually. The nail may be driven almost all the way with one blow, but several lighter taps are necessary to finish the job. Another thing," continued the old carpenter, "the beginner generally tries to drive his nails as perpendicularly as .possible. This is another error, for a nail ■driven a little diagonally holds the parts together much more firmly than one driven perpendicularly. And in driving a nail diagonally it is ever more necessary to proceed 'with gentle taps, for hard blows inevitably displace the surfaces that are to be held together."

BEGINNING OF IKON. It is commonly ibelieved that the use of iron commenced in either Africa or Asia. The latest investigatiqns prove that it was not worked in Egypt until the ninth century before the Christian era, or in Libya until 450 8.C., that the Semites adopted its use still later, and that it has been known in Uganda only within the last five or six centuries. In China iron is first mentioned in 400 B.C. Bronze weapons were employed in China until 100 A.D., and in Japan until 700 A.D. According to a Mr. Ridge way. who has investigated this subject, the metallurgy of iron must have originated in Central Europe, especially in Noricum, which approximately represented modern Austria and Bavaria. Only at Hallstadt and in Basnia and Transylvania, from which countries the Achaians and Dorains are supposed to have migrated to Greece, are found evidences of a gradual introduction of iron, at first as an ornament applied to the bronze which it ultimately Everywhere else iron was introduced suddenly, a fact which implies a foreign origin. He says that meteroric iron was known in Egypt in remote antiquity, but no dombt it was worked as flints were worked, by cutting or chipping, and was not smelted. In other words, it was the metallurgy, not the knowledge, of iron that originated in Central Europe.