A Rejoinder to Criticism on Hypothesis. — Spencer, in 
Omitting- all the evidential facts bearing Upon these fea- 
tures. Dr. Dall tells us that he is still "convinced" that they 
can be otherwise explained, without suggesting in what man- 
ner, lie fortifies himself with the opinions of his junior col- 
leagues, claiming that they throw "much more light on the 
subject," of which 1 can find none. Yet he passes over the 
testimony of other widely separated, but actual investigators 
of the subject. lie prominently introduces several irrelevant 
problems, which are not validly pertinent to my hypotheses, 
and with which I have no occasion to disagree, and these he 
discusses in such a manner as would appear to me to carry 
the implication that he has removed by eounter evidence the 
supports of my hypothesis, which implication cannot for a 
moment be allowed to pass unquestioned. In only one case 
does he raise a valid objection, w'hich is easily explained not 
only by my facts, but also by those of another who is a dis- 
tinguished authority. Finally he proceeds to shatter all phys- 
ical investigations on the subject by a dogmatic pronuncia- 
mentum, which together with his treatment forces me to reply. 
And in order to make this reply intelligible, I must give a 
lengthy citation from Dr. Dall's paper, as follows : 
1. "Dr. J. W. Spencer has propounued some ven- startling hypotheses, 
involving the elevation of some of the Antilles and Florida many 
thousands of feet, and their submergence within a comparatively recent 
period of geological time. 
2. "By the researches of Prof. R. T. Hill and Mr. T. \V. \'aughan 
much more light has been thrown on the subject. 
3. "I am entirely unable to accept Dr. Spencer's hypotheses, while 
admitting many of the facts he brings forward, I am convinced that they 
admit of some other explanation. We find in the Oligocene of Bowden 
land shells belonging to groups peculiar to and now inhabiting the island 
of Jamaica, which is sufiicient evidence that since the era during which 
the Bowden marl was deposited the island has never been entirely sub- 
merged. With Cuba it may be different, though I can hardly bring 
myself to believe that the peculiar land shell fauna which is so char- 
acteristic of that island can have been evolved since the Pleistocene. 
4. "The proximity of Cuba to Florida and the fact that the adjacent 
portions are composed of organic limestones, which has long been 
known, led to the very natural, but erroneous inference that Cuba and 
the peninsula were formerly continuous, and that the Florida straits had 
been cut between by the erosion due to weather and streams, and sub- 
sequently by the gulf stream. 
