1810.] 
nicates, “ that the simple catenaria is of 
no use in determining the relations of an 
arch,” when, at the same time, he fancies 
the whole Emerson theory is ‘‘ legiti- 
mately deduced from a. remark of Dr. 
Gregory:” neither may he be able, to 
translate the parts which he quotes from 
Dr. Gregory into good English, although 
ke knows the Greek alphabet; perhaps 
he thought proper to follow literally Ho- 
race’s precept: 
Nec verbum verbo curabis reddere fidus 
Interpres. 
He may not be able to understand how 
far the mechanical mode of determining 
tne hne of road-way by-~- suspending 
weights froma chain, and the Emerson 
theory, agree ; nor the difference between 
this experiment and when the weight is 
wholly in the links: and although he has 
read Mr. O. Gregory’s Mechanics, those 
important parts which have been taken 
from professor Robson, may have 
escaped his observation. He may not 
have found out, that, exactly that part of 
the semi-circle which, by the Emerson 
theory,* cannot be used, viz. the two 
sixty degrees next the springing, almost 
iuvariably compose the vaultings of the 
Gothic buildings; and that part, viz. the 
thirty degrees on each side the vertex, 
which, by the Emerson theory, is the only 
part that can be used, was never used by 
the Gothic architects. . 
extrados affixed to a section of the vault 
of King’s-college Chapel, Cambridge, 
will be an entertaining diagram at the 
whist-table, to shew them how ignorant 
the builders of the vault of King’s-colleze 
Chapel were of the Emerson theory: 
if miracles were not over, it might be 
mathematically proved by this theory, 
to be sustained by the Virgin Mary and 
St. Nicholas. 
Philo-veritas may not perceive that 
professor Robson introduced ~ this 
theory into the Supplement to the En- 
cyclopedia Britannica, with a view to 
shew how simply it might be. confuted, 
and how it violated common sense and 
uniform experience. Philo-veritas says, 
that “the haunches of an arch sink ;” 
they must be arches built after the 
Emerson theory, which, to be mathema- 
tically in equilibration, must literally 
prick the very heavens; and the haunches 
of which must bear as much fat 
mould as may be contained in the land 
of Philo-veritas’ fat benefice. There is 
Pr eee 
* See page 26, Principles of Bridges, Ynd 
edition, ) 
Lapicida on the Emerson Theory of Arches. 
The Emerson’ 
is 
another circumstance which your corre- 
spondent seems not to have discovered,” 
that Dr. Hutton, in the letters in your 
Mayazine, in answer to your review of 
his Principles of Bridges, and those of 
the Monthly Review, has virtualiy reline 
quished the theory; and he has left the 
“ promised improved edition,” the 
nonumgue prematur in annum ‘* having 
long elapsed, to those who justly think 
that the aud, which so eminent a mas 
thematician has been in, will not soil 
them.” It is hard to kick against the 
pricks.” 
Philo-veritas forgot to account for the 
catenarian arch being equally thick 
throughout, and at the same time having 
a horizontal extrados; or the amusing 
surprise professor Robsont gives his 
readers upon discovering this phenomes 
non. It may be hoped that Philo-veritas 
will examine the report again to which 
he alludes, particularly that part by 
professor Robson on Mansard roof, he 
will learn something respecting the 
‘ sinking at the haunches:” perhaps Dr. 
Milner’s report may amuse him. The 
opinions of fifteen out of the seventeen 
who gave their opinions in that report, 
are not very flattering to the theory of 
equilibration. Philo-veritas, next wume 
he writes, will do well to take the name 
of Pseudo-veritas. Is it intended by the 
disciples of the Emerson theory to 
assert, that Dr. Gregory pretends that 
the catenaria 1s the best form for an arch 
of a bridge, and that he pretends it in the 
passage, “ Ht cujus-cungue,’ &c? The 
enemies of the Emerson theory would 
rejoice to see this avowed, 
In regard to the question of equal 
spheres, it 1s necessary only at present 
to observe, that it may be proper in pure 
mathematics to be positive, but in mixed 
mathematics itis nut philosophical. ‘SJthe 
complex diagram mast be very simple to 
-any one who was, acquainted with Dr. 
Gregory’s paper: but Philo-veritas 
attaches no value to it, otherwise he 
would have discovered that the first sens 
tence.in Lapicida’s quotation was non 
sense, and consequently not a true trans 
lation. It might have been expected 
that one who had acquired reputation 
for learning in his college, would have 
been ashamed to read Dr. Gregory’s 
paper through a translation, or at least 
not until he bad examined it with the 
original: see Ex Mechanicis, &c. Why 
has not your correspondent given some 
* See Ency. Brit, Supp. page 26. 
information 
