Apbil 21, 1882.] 



♦ KNOWLEDGE ♦ 



537 



q : 



^ I. 





a 



E ' 



. S-. 



So 

 B 



to g 



Mt3 



a B 



".3 3 



.2 ic 



NEW METHOD OF FORECASTING STORMS. 



IN the course of his investigations on the behariour of magnets, 

 Father Secclii, the well-known Italian physicist, perceived the 

 interesting fact that the disturbance of niafiTiotic equilibrium which 

 attends magnetic storms, and usually accompanies displays of 

 Aurora Borealis, is also exhibited under the influence of cyclonic 

 systems, or what are commonly known as the approach and passage 

 of storms of wind and rain. 



JI. Descroix, llotoorological Dii'ector of Montsouris Observatory, 

 Paris, has recently been following up the pregnai^t hint bequeathed by 

 Father Secchi, and has published, in a recent Bulletin of the French 

 Meteorological Society, his general conclusions. Fully six days 

 before the arrival on the western shores of Europe of a cyclonic 

 disturbance, the several magnetic needles (of declination, inclina- 

 tion, and horizontal force) showed decided symptoms of sympathy 

 witli the coming storm. The earth acts as a telegraphic conductor 

 in announcing the approach of the gale. 



SI. Descroix is at present engaged in the endeavour to express in 

 accurate formnlte the laws governing the action of distant cyclones 

 on the magnetic needles, and we may hope at no very distant day 

 to possess useful and accurate information on tliis important 

 subject. 



ICEBERGS. 



ICE-FIELDS and icebergs appeared off Xewfouudland nearly two 

 months earlier than usual this season. The steamship Averill, 

 from West Hartlepool, England, was the first to tell of ice on the 

 Banks, having sighted it in latitude 47^ north, longitude 47° west, 

 on Felj. 11. She was surrounded for twelve hours. Nearly every 

 day since then the arriving steamships have reported ice, which 

 has drifted to the southwai-d and eastward. The steamship Van- 

 dalia, which passed around the ice-field, Feb. 11, sighted two 

 towering bergs about 60 feet in height and 120 and 200 feet on the 

 sides. 



The White Star steamship Germanic, from Liverpool, reports 

 that on March 1, in latitude 43° 35' north, longitude 49° 10' west, 

 she was confronted with a great field of ice, and did not reach 

 clear water for two hours. This seems to indicate that the ioo 

 extended for at least twenty-five miles. As no icebergs were seen, 

 it is probable that in floating 205 miles to the southward and about 

 90 miles to the eastward, they crumbled under tlie influence of 

 warmer waters. The Belgian steamship Helvetia encountered afield 

 of ice and icebergs, and was forced to run to the southward 80 miles 

 before she got to clear water. The steamahip Nev: Tork, from 

 Bristol, fell in with large fields of ice and bergs, varying from 60 to 

 300 feet in height, and ran a south-south-east course for 160 miles 

 at slow speed before she found open water. The British steamship 

 Milanese, from Boston, February 18, for London, was so seriously 

 damaged by the ice on the Banks of Newfoundland, that she put 

 back to Halifax for repairs. — Scientific American. 



COPYING DRAWINGS. 



TILHET'S method of copying drawings in any desired colour is 

 thus described in the Polytechnisches Notisblatt : "The 

 paper on which the copy is to appear is first dipped in a bath con- 

 sisting of 30 parts of white soap, 30 parts of alum, 40 parts of 

 English glue, 10 parts of albumen, 2 parts of glacial acetic acid, 10 

 parts of alcohol of 60', and 500 parts of water. It is afterward put 

 into a second bath, which contains 50 parts of burnt umber ground 

 in alcohol, 20 parts of lampblack, 10 parts of English glue, and 10 

 parts of bichromate of potash in 500 parts of water. They ore now 

 sensitive to light, and must, therefore, be preserved in the dark. 

 In preparing paper to make the positive print, another hath is made 

 just like the first one, except that lampblack is substituted for the 

 bui-nt umber. To obtain coloured positives, the black is replaced by 

 some red, blue, or other pigment. 



In making the copy, the drawing to be copied is put in a photo- 

 graphic printing-frame, and the negative paper laid on it, and then 

 exposed in the usual mannei-. In clear weather an illumination of 

 two minutes will suflice. After the exposure the negative is put in 

 water to develope it, and the drawing will appear in white on a 

 dark ground ; in other words, it is a negative or reversed picture. 

 The paper is then dried and a' positive made from it by placing it 

 on the glass of a printing-frame, and laying the positive paper 

 npon it and exposing as before. After placing the frame in the sun 

 for two minutes, the positive is taken out and put in water. The 

 black dissolves off without the necessity of moving it back and 

 forth. 



