Chemistry and Physics. 308 
the absence of the requisite structural conditions for preserva- 
tion of moisture, as well as the excess of carbonate of lime in 
their soils. The difference in fertility between the sandy loams 
of the Lower Cross Timbers and the dirty sands of the Upper, 
accounts for the varietal differences of their respective floras. 
The flora of the Cross Timbers is by no means confined to those 
two areas, but exist in smaller tracts wherever the soil and struc- 
ture are favorable. In fact the finest development of the flora 
has been observed in some of these local patches. | 
The Cross Timbers end so abruptly upon the maps to the 
south and north for two reasons. To the south the arenaceous 
strata are either covered by higher strata, or washed away 
entirely; the northern termination is usually placed at Red 
River, because of the absence of correct topographical knowledge 
concerning its extent in the Indian Territory. Itis well known, 
however, that they extend into that region, and it is probable 
that the two members there merge into one—the surface becom- 
ing more fertile, and the rains more abundant and regular, so 
that the timber’s growth is not necessarily confined to the 
sandy soils. 
It is also now evident that many important differences in the 
two members of the Cross Timbers are seen in 'l’exas, and that 
they can no longer be treated alike from an agricultural or 
geologic standpoint, the lower one being far more fertile and 
better adapted to human habitation than the upper, which is 
mostly an arid and sterile region. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND PHYSICS. 
1. On the Phosphorescence of Alumina.—EK. BecQquEReE has 
replied to de Boisbaudran concerning the phosphorescence of 
alumina. He had examined this earth in 1859 and had found 
that the phosphorescent light emitted by it was red and that it 
gave a characteristic spectrum. Precipitated alumina imperfectly 
calcined emits sometimes a greenish light in the phosphoroscope; 
but when heated to 1200° or 1400°, the light it gives is always 
red. Moreover the author had observed the influence of other 
substances and especially of chromium, upon the intensity of the 
light, rubies being more luminous than white corundum, though 
the composition of the light is the same. He has now repeated 
his experiments, using for the purpose substances furnished by 
de Boisbaudran himself and therefore identical with those experi- 
mented upon by the latter.* Fragments of this alumina, con- 
* See the February number of this Journal. 
