668 
foot of that part of the Cordilleran mountain 
series called Sierra de Sandia and bordering 
exactly the Rio Grande del Norte; just where 
is situated the town of Albuquerque and the 
villages of Alameda, Sandia and Bernalillo. 
Such erroneous volcanic geography has never 
been given in a map of the United States even 
on the most rough sketch. 
The group of craters of the Cerrito was first 
discovered by the present writer in 1853, and re- 
corded as such, on the geological map of New 
Mexico, 1857, published in Zurich, Switzerland, 
in Geology of North America. They occupy a 
part of the mesa existing between the southern 
system of the Cordillera called the Santa Fé 
Mountains and the northern end of the Sierra de 
Sandia, nearer to the city of Santa Fé than of 
Albuquerque, and close to the railroad station 
called Lamy. The Cerrito lie between Galisteo, 
Cieneguilla and Lamy. On the sketch map of 
Mr. Hill, the crater of the old voleano called 
Cerrito ought to be placed just near the head 
waters of the Rio Pecos, a little south of the 
Santa Fé Mountains and northeast of the Sierra 
de Sandia; and the three black discs of Albu- 
querque, Sandia and Bernalillo, on the eastern 
side of the Rio Grande, scratched out. 
JULES MARCOU. 
GLACIAL STRIA. 
To THE EDITOR OF SCIENCE: While stroll- 
ing over the low hills adjacent to the Delaware 
river in Northampton county, Pa., I found un- 
mistakable glacial stris, at least four miles 
south of the front of the terminal moraine, as 
commonly defined. 
Three parallel scratches, with traces of a 
fourth, on the sloping side of a shelf of lime- 
stone that had just been uncovered from under 
what seemed a slight bed of true till, and with 
a direction 8. 20 W., made a mistake of judg- 
ment, it seems to me, impossible. Therepeated 
occurrence. of such ice traces throughout this 
county to a distance of at least twenty miles 
south of the moraine most certainly opens for 
investigation the question of the southern 
limit of glacial ice. 
Yours, 
ALBERT G. RAv. 
BETHLEHEM, September 15, 1897. 
SCIENCE. 
[N. 8. Vou. VI. No. 148. 
THE ALLEGED EXTINCTION 
SCENT. 
PROFESSOR W. K. Brooks contributed to 
this JOURNAL some time since (February 1, 1895) 
an interesting article entitled ‘An Inherent 
Error in the Views of Galton and Weismann on 
Variation.’ The argument of this paper was 
based on the alleged necessary extinction of 
lines of descent. Thus Professor Brooks writes : 
OF LINES OF DE. 
“*Of all the individuals of a species which lived at 
a given period, very few would have descendants at 
a later period.’”? ‘‘Most of the individuals in each 
generation must fail to perpetuate their lines to remote 
descendants.’’ ‘‘If a city like Baltimore, where 
the strangers to each one of us cutnumber our ac- 
quaintances a thousand fold, could be quarantined 
against people from outside for a thousand years, 
each generation would be like the present one so far 
as known relations are concerned, although at the 
end of the period the inhabitants would certainly not 
be descended from the Baltimorians of our day, but 
from only a very few of them. Most of our lines 
would be extinct.”’ 
I return to the subject because Professor 
Brooks’ statements carry great weight in a sub- 
ject important for theories of heredity and evo- 
lution, and it seems to me that they con- 
tain ‘an inherent error.’ Family names will be- 
come extinct, as shown by Mr. Galton, but not 
lines of descent that have persisted for several 
generations. Ifthe present population of Bal- 
timore is to remain stationary, some of the in- 
habitants having no offspring, the others must 
on the average have more than two. If, for 
example, we simplify the problem by supposing 
one-half of the population to be sterile, and 
each of those who are fertile to have four off- 
spring who survive to maturity, then only one- 
sixteenth of the fertile parents would have no 
descendants in the third generation. Of the bal- 
ance only one line in 256 would become extinct 
in the fourth generation, one in 65,536 in the 
fifth, and one in 4,294,967,296 in the sixth. 
With families of variable size, etc., the calcula- 
tions would become intolerably complex; but 
in any population not decreasing in numbers 
the descendants of each individual tend to in- 
crease in a geometrical ratio and cannot become 
extinct after several generations. If King 
Alfred and King Alfred’s barber had lines of 
descent lasting several generations, we are each 
