o66 J'ura^ Neocomian and Chalk of Arkansas. — Marcou. 
escaped his notice. In my : "Reconnoissance geologique au 
Nebraska" {Bulletin Soc. Oeol. France, vol. xxi, p. 145), I 
say : "In my visit at the Verygood's quarry, I was struck with 
the extremely chalky lithological characters of the rocks, 
which have reminded me more than anything I saw before in 
America of the chalk of the Paris and London basins." And 
three years later, at the meeting of the 19th of Nov., 1886 of 
the same society in Paris, in reading my paper : "Le terrain 
Cretace des environs de Sioux City de la mission des Omahas 
et de Tekama, sur les bordsdu Missouri" {Bulletin Soc. Geol. 
France, vol. xxiv, p. 56), I took the precaution to carry with 
me pieces of rough chalk taken near Sioux City, and I drew 
on the blackboard Aviththem the three sections which accom- 
pany the paper, and at the end I said, writing with that chalk, 
"Craie d'Amerique," that in order to prove the constancy of 
lithological characters on vast surfaces of the earth, I had 
used only American white chalk that evening for my commu- 
nication before the Geological Society of France. All the 
members applauded loudly my practical remark. 
In finishing my review of professor Hill's work, I must 
mention the excellent "Geological Map of southwestern Arkan- 
sas" at the scale of 1 : 202,752, which accompanies the volume. 
The legend comprises six divisions, beginning with the allu- 
vium, then the plateau gravel, the Tertiary, upper Cretaceous, 
lower Cretaceous and Trinity divisions. So that according 
to professor Hill, the Trinity is not Cretaceous ; then he ought 
to have used another color than green. It is the only criti- 
cism to be made of that beautiful map ; the Trinity formation 
being Jurassic ought to be colored in pale sky blue, which 
would have improved the appearance of the map. The limits 
of the formations are very distinct, and the distribution of the 
Trinity division shows a break of some sort between it and 
the lower Cretaceous, which exists only at a single spot, at 
Cerro Gordo. In a country so wooded and unhealthy as 
southern Arkansas, explorations are very difficult and even 
dangerous on account of the malaria, and professor Hill has 
not an easy task. 
On the whole, volume ii of the Arkansas geological report 
for 1888 is a most creditable work, which reflects honor not 
only on its author, professor Robert T. Hill of the University 
of Texas, by far the best practical geologist who lias ever 
