1875.] 
or thick” margin, et vice versa, which 
implies an active “retournement” of 
the wing. 
But this figure must be looked for 
in the article of the “* Transactions of 
the L. S.,” published before Mr. Pet- 
tigrew’s complaints and before my 
answer. It is no more to be found 
in the posterior publications. 
This figure, without doubt, has 
been lost. It has even been forgotten 
to such an extent that when Mr. 
Pettigrew traces afterwards the tra- 
jectory of an inseét’s wing, he points 
his guiding arrows not in the same 
direction as formerly, but in the direc- 
tion according to which I had always 
pointed them. 
With reference to the flight of 
birds, my accuser piles up quotations. 
He compares texts, and every time 
he meets with similar expressions in 
the English and French books, he 
raises a cry of plagiarism, as if it 
were possible to treat of the flight of 
birds without speaking of wing, 
a kite, inclined plane, sculling, 
Cc. 
This overflowing copiousness of 
Correspondence. 
547 
quotations has the effect, perhaps not 
intended, of fatiguing the mind and 
misleading the judgment of the 
reader. Would it not be much more 
for the purpose to take Mr. Pettigrew’s 
own opinions on the debate ? 
Mr. Pettigrew, in his last work 
(‘‘ The Animal Locomotion’’), devotes 
Io pages to impugn my theory on the 
flight of birds, and a special chapter 
to show to what extent his own 
theory differs from it. This work of 
Mr. Pettigrew, as well as my book 
entitled ‘‘ Animal Mechanism,” hav- 
ing been respectively translated in 
both languages, every one can com- 
pare them, and by so doing, will 
ascertain that two authors could not 
easily have treated the same subject 
with more widely dissimilar methods 
and arrived at more different conclu- 
sions. 
But those who have only read the 
article in the ‘Quarterly Journal’ 
may form an estimate of me which I 
am anxious to correct.—Believe me, 
dear sir, yours very respectfully, 
MareEy. 
Professeur au College de France. 
