INDUSTRIAL PROGRESS DURING THE YEAR 1876. Lxiii 



the rotatory power of quartz upon ultra-violet liglit, in which they 

 used very successfully the new fluorescent eye-piece for the spectro- 

 scope recently devised by Soret. They succeeded in measuring the 

 rotation of rays as far as the line N, and found that it increased 

 from 51.22 at H to 55.88 at L, 59.03 at M, and 64.41 at N. The the- 

 oretical values calculated from Boltzmann's formula agreed well 

 with these. Subsequently CrouUebois has stated that he had made 

 similar measurements, extending as far as the line O. 



Nipher has communicated to Nature some ingenious optical exper- 

 iments, essentially physiological in character. Roll ujd a sheet of pa- 

 per, look through it, with one eye focused on some object beyond. 

 On placing the hand by the side of the distant end of the tube, it 

 will seem as if the hand were perforated and the sides of the tube 

 transparent. If a drop of ink be placed on the hand, it will appear 

 in the inside of the tube, but the hand itself will be invisible. This 

 tube arrangement, used with both eyes, is excellent for viewing com- 

 plementary colors. 



ELECTRICITY. 



Sandoz has examined four of the new Jamin permanent magnets 

 of laminated steel with a view to ascertain whether their force varied 

 with time whetfier the armature was attached or not, and also wheth- 

 er sudden rupture diminished the portative force. The magnet em- 

 ployed weighed 411 grammes, and its armature 69 grammes. Its 

 maximum lifting power was 9.3 kilogrammes, or nearly twenty- 

 three times its own weight. He finds that these magnets gain 

 rather than lose by time, and that whether they are kept armed or 

 not ; and sudden rupture rather increases their power to receive 

 charges. 



Camacho has described a new form of electro-magnet, in which, 

 instead of a bar of iron, the core is made up of a number of concen- 

 tric tubes of iron, around each of which a coil of wire is wound. In 

 one experiment such a magnet, charged with the same battery, lifted 

 five times the weight which was raised by a precisely similar magnet 

 constructed on the old plan. In a subsequent paper Du Moncel has 

 communicated to the Academy some results he obtained with this 

 magnet, which are analogous to those made by him in 1862. He 

 shows that the increased power obtained in these magnets is due to 

 a superposition of the magnetic effects by the enveloping cores. 



Jamin has re-observed and extended the curious fact stated by 

 Haldat that iron filings, inclosed in a brass tube and compressed, 

 retain their magnetism permanently. Tubes thus made were shown 

 the Academy, eight or ten centimeters long and three in diameter, 

 which attracted iron filings at least as strongly as steel bars of good 

 quality of the same size. Filings of pure soft iron showed the same 

 result, as also did iron reduced by liydrogen. 



