100 Scientific Intelligence. 
white bodies act upon light. The peculiarities which distinguish rays of 
heat reflected from metals from those which are not reflected, with re- 
spect for instance to their capacity to pass through diathermanous bodies, 
depend upon the nature of the source of heat to such a degree e that dif 
_ ferences which are strikingly marked in the case of the sun’s heat, are di- 
minished in the rays of a Locatelli lamp, sy disappear completely with 
e heat of a dark heated metallic cylin 
The quality of the metallic surface sesso as it determines . diffuse 
or a regular reflection has such an influence as either to permit the dif 
ferences mentioned to be exhibited to their full exte ent, or again *e ae 
pear to such a degree that the rays are not to be distinguished from each 
other before and after reflection. 
The same is true of a change in the angle of incidence. As this grad- 
ually permits the diffuse reflection of a rough metallic plate to pass into 
regular reflection, = a constantly i increasing intensity, as the rays be- 
me more and more obliquely incident, so it also diminishes the differ- 
ences between the reflected and non-reflected heat, till both at last exhibit 
a 
extrem 
liquid renders its existence a very delicate and valuable indication of the 
presence of didymium. The salts of lanthanum and cerium produce no 
similar effects. One part of sulphate of didymium dissolved in 1 
parts of water showed the line in the yellow asa distinct =o 
when half an inch of the solution was looked through. The presence of 
other bodies does not interfere with the application of the iar so far ab 
least as other metallic solutions have been studied — Quarterly Journal 
of the Chemical Society, No. xxxix, 219. 
oe os 8 employment of the salls of alumina in the analysis of plants. 
ER has pointed out the superiority of alumina over hydrate 
of rit of "lead for the separation of the proximate constituents of plants 
The e first place remarks that organic substances may be 4 
vided into two classes with reference to their behavior toward alumina. 
Many coloring matters, as well as other substances, are presipitated by 
alumina from their solutions, while others on the contrary 2 
Alumina rps gives us a method of separating tie one class from the 
other, recipitates are less gelatinous than alumina and more 
washed oat te many cases a solution of alum may be added directly to 
method, an aqueo’ 
lution of alum and then w ae ammoni es a faw sobhend precipi 
The filtered solution is wine-yellow. The seine neatrliaed ith aceti¢ 
acid and evaporated to dryness in a water-bath mass contai taining 
oe sulphates of potash and pease a little mun as ammonia and 4 
esculin. This may be separated by boiling with a little strong alco 
hol and filtering. The ssculin i on evaporation and after 4 
