470 Scientific Intelligence. 



tares the quartz is attacked by phosphoric acid ; according to 

 Prof. Myliiis, crystallized silicic-phosphoric acid is formed — this 

 also happens with the melting of phosphoric-ammonia-magnesia 

 in phosphoric acid determinations. 



Quartz at highest temperatures is not attacked b}^ metals free 

 from oxides. It allows a slow passage of hydrogen. This is much 

 less than in the case of platinum and enters at a higher tempera- 

 ture than in the case of the latter. Shenstone states that a mix- 

 ture of nitrogen and oxygen in quartz vessels, heated to the melt- 

 ing point of platinum, is converted into hj^ponitrous acid. The 

 temperature of melting of quartz is about 2000°. The coefficient 

 of expansion is extraordinarily low — far lower than with any 

 known material — and makes the quartz very suitable for thermom- 

 eters which are now constructed by Dr. Siebert and Kuhn. 



If one passes an electric discharge through a rarified quartz 

 tube a strong odor of ozone is noticed. This is a ver}^ noticeable 

 phenomenon with Arons mercury lamp enclosed in a quartz vessel. 

 It is impossible to remain long near such lamp. This behavior of 

 quartz was first noticed by Lenard, Ann. d. Physik, 503, 1900. — 

 Deutsche Mechaniker Zeitung, Oct. 1, 1903. j. t. 



6. Absorption of Ultra -Violet Mays hy Ozone. — It is well 

 known that the earth's atmosphere absorbs the ultra-violet rays 

 below A = 3000. W. N. Hartley found an absorption band of 

 ozone at a mean wave-length of A = 2560. Edgar Meyer has 

 taken up this subject and has obtained quantitative results by a 

 new method. The new feature of the method consists in the 

 employment of the photoelectric photometer of Kreusler to deter- 

 mine the regions of absorption. This photometer is described in 

 the Ann. der Phys., vi, p. 398, 1901. It was found that the 

 extinction coefficient of ozone increased with the amount of 

 ozone, and Hartley's absorption band was rediscovered; but at a 

 mean wave length of A = 2580. 



Since the earth's atmosphere strongly absorbs the ultra-violet 

 rays, Meyer discusses the question whether this absorption is 

 largely due to ozone. A. Levy concludes from his ozonometric 

 measurements, extended over twenty years, that lOO'^^ of air con- 

 tains I'Go'"^ of ozone. Me3^er takes this result, makes the 

 assumption tl3t it is the ozone which absorbs the short waves, 

 and computes the energy disti'ibution in the solar spectrum by the 

 aid of Planck's formula. The graphical representation of the 

 results show that in the region 2200 there is more than twice the 

 energy that appears at wave-length 2500. The quantitative 

 determination of the absorption bands of ozone are more con- 

 clusive than the determination of the question whether the ozone 

 is chiefly instrumental in the absorption of the short waves of 

 \\^i.~Ann. der Physik, No. 12, 1903, pp. 849-85^. J. t. 



7. Induced Thorium Activity. — Thorium possesses, in com- 

 mon with radium, two kinds of radiation; the straight line radia- 

 tions and the so-called emanation. Rutherford attributes the 

 induced activity to this emanation. If one brings the source of 



