238 FRAGMENTS OF SCIENCE. 



ter are arranged together. In 1853 I also published a 

 paper &quot; On Molecular Influences,&quot; in which common heat 

 was made the explorer of organic structure. In the &quot; Ba- 

 kerian Lecture,&quot; given before the Royal Society in 1855, 

 the same idea and phraseology crop out. The Bakerian 

 Lecture for 1864 bears the title &quot; Contributions to Molec 

 ular Physics.&quot; And all through the investigations which 

 have occupied me during the last ten years, my wish and 

 aim have been to make radiant heat an instrument by 

 which to lay hold of the ultimate particles of matter. 



The labors now to be considered lie in the same direc 

 tion. In the researches just referred to, tubes of glass and 

 brass were employed, called, for the sake of distinction, 

 &quot; experimental tubes,&quot; in which radiant heat was acted 

 upon by the gases and vapors subjected to examination. 

 Two or three months ago, with a view of seeing what oc 

 curred within these tubes on the entrance of the gases or 

 vapors, it was found necessary to intensely illuminate their 

 interiors. The source of illumination chosen was the elec 

 tric light, the beam of which, converged by a suitable lens, 

 was sent along the axis of the tube. The dirt and filth in 

 which we habitually live were strikingly revealed by this 

 method of illumination. For, wash the tube as we might 

 with water, alcohol, acid, or alkali, until its appearance in 

 ordinary daylight was that of absolute purity, the delusive 

 character of this appearance was in most cases revealed by 

 the electric beam. In fact, in air so charged with sus 

 pended matter as that which supplies our lungs in London, 

 it is not possible to be more than approximately clean. 



Vapors of various kinds were sent into a glass experi 

 mental tube, a yard in length, and about three inches in 

 diameter. As a general rule, the vapors were perfectly 

 transparent ; the tube, when they were present, appearing 

 as empty as when they were absent. In two or three cases, 

 however, a faint cloudiness sho\ved itself within the tube. 



