Intelligence and Miscellaneous Articles. 159 



projection in splinters. Boracic acid poured upon water is suddenly 

 pulverized ; but with oil little masses with short steins are obtained 

 which explode under the same conditions as Prince Rupert's drops. 



A chilled plate of boracic acid with parallel surfaces acts on pola- 

 rized light like chilled glass ; but while the latter loses this property by 

 annealing, boracic acid retains it with singular tenacity. Some frag- 

 ments of chilled boracic acid were placed in the annealing-furnaces 

 of M. Feil, kept at a red heat for fifteen hours, and submitted to a 

 slow cooling of several days. They acted on polarized light as ener- 

 getically as before, although some lumps of glass of 60 kilogrammes 

 placed beside them were completely annealed. 



On placing some rather large pastils of chilled boracic acid in 

 water at the temperature of from 15° to 20°, hydration is observed 

 to take place in layers, producing a veritable exfoliation. The inner 

 layers, in undergoing hydration, increase more in volume than the 

 outer ones ; hence results a lifting of the exfoliated portions, which 

 takes place nearly symmetrically with respect to the middle layer 

 towards each surface ; and the plate of boracic acid, after hy- 

 dration, has the appearance of two caps tangent by their convex 

 surfaces. 



This deformation is constant, and does not depend on the form 

 of the fragment of boracic acid operated on. It proves that the two 

 surfaces are chilled in opposite directions ; it shows, next (and this 

 is the most interesting fact), that the portions already dilated by 

 chilling do not undergo through combination with water the same 

 augmentation of volume as the parts less chilled or which are not 

 chilled at all. In a word, hydration produces in boracic acid aug- 

 mentation of volume ; nevertheless, if tempering has already given 

 rise to an increase of volume, hydration takes place, but there is not 

 the same change of volume. These facts appear to be intimately 

 connected with those described by M. Berthelot under the name of 

 kenomerie. They confirm, as regards boracic acid, the structure 

 which I have attributed to chilled glass. — Comptes Bendus de VAcad. 

 des Sciences, vol. lxxxi. pp. 80, 81. 



THE DISCOVERY OF A METHOD OF OBTAINING THERMOGRAPHS 

 OF THE ISOTHERMAL LINES OF THE SOLAR DISK. BY ALFRED 

 M. MAYER. 



On June the 5th, 1875, I devised a method for obtaining the 

 isothermals on the solar disk. As this process may create an 

 entirely new branch of solar physics, I deem it proper that I 

 should give a short account of it in order to establish my claim as 

 its discoverer. 



In the American Journal, July 1872, I first showed how one 

 can, with great precision, trace the progress and determine the 

 boundary of a wave of conducted heat in crystals, by coating 

 sections of these bodies with Meusel's double iodide of copper and 

 mercury and observing the blackening of the iodide where the 



