270 SCIENCE. 
differential calculus, the all-important dis- 
covery of gravitation, of the laws of planet- 
ary motion, of the circulation of the blood, 
of the measurement of the velocity of light. 
To theeighteenth century we refer the more 
important of the.earlier steps in the evolu- 
tion of the steam engine and the founda- 
tion of both modern chemistry and electrical 
science. This completes the list. Count- 
ing all these inventions and discoveries as 
separate we get sixteen. Wallace places 
the barometer and thermometer under one 
number and thus makes a total of fifteen. 
What is there to be added to this list? 
Some would urge that Jenner’s discovery 
should be included here, but this claim 
Wallace would indignantly deny. 
In making such a list it is evident that 
the personal equation of the author needs 
to be recognized, and different orders of ar- 
rangement, even if the elements were the 
same, would be assigned by different stu- 
dents. At any rate, something like this is 
the list of what the race has gained in 
science since it first came toitself, up tothe 
year 1800. The greatest steps have cer- 
tainly all been counted. 
And now what has the record been since 
1800? How does the 19th century compare 
with its predecessors? A brief examination 
will show that in scientific discovery and 
progress it is not to be compared with any 
single century, but rather with all past 
time. In fact, it far outweighs the entire 
progress of the race from the beginning up 
to 1800. Counting on the same basis as 
that which he had previously adopted, Wal- 
lace finds 24 discoveries and inventions of 
the first-class that have had their origin in 
the 19th century, against the 15 or 16, 
already enumerated of all past time. This 
is not a proper occasion to review, compare 
and set in order the several elements of 
this glorious list, but let me simply recall 
to your minds a few of them. 
Of the same rank with Newton’s theory 
[N.S. Von. X. No. 244, 
of gravitation, which comes from the 17th 
century, stands out the doctrine of the cor- 
relation and conservation of forces of our 
own century, certainly one of the widest 
and most far-reaching generalizations that 
the mind of man has yet reached. Against 
Kepler’s laws from the 17th century we 
can set the nebular theory of the 19th. 
The telescope of the 17th is overbalanced 
by the spectroscope of the 19th. If the first 
reveals to us myriads of suns, otherwise 
unseen, scattered through the illimitable 
fields of space, the second tells us what sub- 
stances compose these suns and maintain 
their distant fires and, most wonderful of 
all, the state in which each exists, whether 
solid or gaseous, and the direction and the 
rate in which each is moving. Of the 56 stars 
whose motion in the line of sight have thus 
far been determined five were determined 
in the Emerson McMillin Observatory. 
Harvey’s immortal discovery of the 17th 
century finds a full equivalent in the germ 
theory of diseases of the 19th. The mari- 
ner’s compass of the 14th century easily 
yields first place to the electric telegraph 
of the 19th, while the barometer and ther- 
mometer of the 17th century are certainly 
less wonderful, though, perhaps, not less 
serviceable, than the telephone and phono- 
graph and Rontgen rays of our own day. 
I need not pursue the comparison ex- 
haustively, but, in addition to the advances 
now enumerated, the great doctrine of Or- 
ganic Evolution, supported especially by the 
recapitulation theory in embryology, finds 
nothing to match with it in broadening and 
inspiring power, in all the past history of the 
race. The samecan be said of the periodic 
law of Mendeljeff in chemistry, of the 
molecular theory of gases, of Lord Kelvin’s 
vortex theory of matter, of the glacial 
period in geology, and of the establishment 
of the origin and antiquity of man, all of 
our own century. 
Nothing can be brought from all the past 
