PHYSICS AKD natural HISTORY OF GENEVA. 295 



gas more dense than oxygen In the second, directing his inquiries to the ex- 

 istence of a body which really absorbs ozone, instead of separating it by absorbing 

 but a part, as is the case with the iodide of potassium, he finds the essence of 

 turpentine to be the most favorable substance for effecting this absorjttion. 

 Ozonized oxygen, when treated with this essence, undergoes a very consider- 

 able diminution of volume, being very nearly double the volume of oxygen ab- 

 sorbed by the iodide of potassium. This would confirm the hypothesis that the 

 molecule of ozone is composed of three atoms of oxygen, and that consequently 

 the theoretical density of ozone is one and a half times that of oxygen. In the 

 sequel he has found in the essence of cinnamon a substance not less favorable 

 than the essence of turpentine for effecthig the absorption of ozone, and com 

 paring the diminution of the ozonized gas, treated with these essences, with the 

 augmentation of volume which the same gas undergoes through the action of 

 heat, he has arrived with more exactness at the conclusion that, in effect, the 

 density of ozone is one and a half that of oxygen. 



M. Delafontaine, (February 1, 1SG6,) after recalling the fact that his pre- 

 vious researches have confirmed those of Mosander, on ythria, terbine, and er- 

 biue, explained how it may have happened that MM. Bunsen and Boehr did not 

 recognize these three earths. His last researches, while confirming his previous 

 inquiries, and consequently also the results obtained by Mosander, have led him 

 to see that MM. Bunsen and Boehr, who deny the existence of terbine, have, 

 notwithstanding, had that substance in their hands, but that they have taken it 

 or erbine. 



Professor Marignac (February 15, 1866) called the attention of chemists to 

 'lie danger arising from the contact of the double salt of the fluoride of niobium 

 ind potassium with the skin. This salt produces an alteration of the cutis, under 

 he form of rubefactions and eruptions, accompanied with itching, which may 

 ast without diminution for six months after the accident. 



Professor Wartmann (May 15, 1866) also drew the attention of the society 

 .0 the dangers of explosion j^rescnted by the oxalate of silver. MM. Marignac 

 and Perrot suggested that the explosions observed by M. Wartmann might be 

 owing to the presence of organic substances mixed with the oxalate. 



NATURAL SCIENCES. 



Geology. — Professor Favre, member of the federal geological commission, pre- 

 sented (January 10, 1866) a geological chart of the environs of Brugg, executed 

 by M. Moesch, and which forms a part of those published by the commission. 



M. de Loriol read a memoir (March 15, 1866) on the uj)fer Jurassic deposits, 

 and particularly those of the environs of Boulogne sur Mer. Both in England 

 and France the marls composed of the Ostrea virgula are usually surmounted by 

 masses of limestone, moie or less compact, sometimes coralline, which are covered 

 in turn by deposits of Purbeck. These formations represent the Portlandian, 

 properly &o called, and, in England, comprise a very special fauna, of which the 

 Trigonia gibbosa is one of the characteristic fossils. At Boulogne are found 

 strata analogous to those of the Purbeck beds, beneath which beds of limestone, 

 sand, sometimes clay, form the equivalent of the English Portlandian, and in- 

 clude several of its characteristic fossils, among others the Trigonia gibbosa. In 

 proportion as we descend into the series of deposits, the species of the English 

 portlandian are found to diminish in number, and those of the kimmeridian to 

 increase. Immediately above the Ostrea virgula marls occurs a bed of limestone 

 bearing the Ammonites gig as, (Zieten,) which terminates the series of strata 

 that may be considered as the equivalent of the English Portlandian, or rather 

 as the upper portion of the kimmeridian group, of which the Portland beds would 

 constitute but a local fades. The inferior layers of this mass have been trav- 

 ersed by the railroad from Boulogne to Calais, in which excavations have brought 



