864 SUMMARY OF CUERENT RESEARCHES. 



views * and produced some specimens in illustration, consisting of 

 five envelopes containing the same address written ly different 

 persons. 



Smoke and Steam under the Microscope.t — L. J. Bodaszewsky 

 calls attention to the rapid oscillatory movements which are disclosed 

 by the Microscope in the smoke of burning paper, wood, cigars, &c., 

 when concentrated sun or electric light is thrown upon them through 

 a lens. The particles are of a spherical form, and they are con- 

 tinually darting against each other, so as to represent very strikingly 

 the motion of gas molecules according to the kinetic theory. Similar 

 movements are observed in the vapour of nitric, sulphuric, and 

 phosphoric acids, sulphur, ammonia, &c., when examined under the 

 Microscope by the light of a glowing platinum wire. 



Microscopical Representation of Physiological Movements.^ — 

 M. Marey has succeeded in a further develojjmeut of the Graphic 

 Method. He has given to the tracing dimensions so reduced as to justify 

 one in neglecting the velocity of the writing pen. Taking for example 

 a sphygmogram or a cardiogram he shows that ordinarily the curves 

 are about 5 mm. high ; supposing that the lever moves very fast and 

 so moves too far, if we reduce the amplitude of the tracing ten times 

 (to • 5 mm.) the effects of the velocity would be so much diminished as 

 to be a hundred times less than with the ordinary instruments. These 

 tracings must, however, be taken on surfaces which move exceedingly 

 slowly, and the details of the curve cannot then be seen by the naked 

 eye. When magnified ten times they can be made out. Experiments 

 thus conducted show that the tracings are identical with those given 

 by the ordinary cardiograj^h and similar instruments, in which, there- 

 fore, one may place complete confidence. 



The microscopic markers can also be used to mark such delicate 

 movements as the vibrations of the blood in the vessels, and they have 

 a practical recommendation in being very portable, and so easily used 

 in medical practice. 



* See Amer. Journ. Micr., vi. (1881) pp. 104-8. (A discussion followed the 

 reading of the paper.) 



t Dingler's Journal. See Journ. Franklin Institute, Ixxxi. (18S1) p. 384. 

 X Comptes Kendus, scii. (1881) pp. 939-41. 



