1822.] 
sentation that Mr. Snodgrasssuggested 
the method of laying blocks in docks, 
and for which Sir Robert Seppings 
received, about the year 1800, a re- 
ward of 1,000/. Mr. Snodgrass, in 
his letter to the East India Company 
in 1806, recommended “that there 
should be a reservoir to fill each dock 
with water, so as to raise the ship on 
high blocks,” and_has made no allu- 
sion whatever to the iron wedge 
blocks in question, which are so easily 
removed, when ships are required to 
be suspended to remedy defects in 
their keels, &c. and are not used for 
the purpose of lifting ships. So much 
for the knowledge and accuracy of 
your correspondent. , 
It will appear by the authorities 
which have been given, that most of 
the principles aforestated have been 
long known and practised, and thus 
become public property; but, if the 
limits of a letter would allow, I could 
show very material modifications and 
alterations in each, as introduced by 
Sir R. Seppings, so as to give them 
the title of inventions. In the hands 
of the persons who preceded him, 
these alterations from the common 
system failed ; under hismanagement, 
and by his improvements, they have 
succeeded admirably ; and it is always 
to be recollected, that it is the whole 
of a machine which is to be regarded, 
not its parts; and that, although we 
cannot create a new mechanical 
power, yet every credit is due to him 
who invents an useful machine by a 
new combination of known principles. 
But I challenge your correspondent 
to bring forward a single authority to 
show, that the manner of putting toge- 
ther the frame timbers,—the diagonal 
trussed frame in the holds of ships,;— 
the trussing between their ports,—the 
combination of thick waterways with 
the beams and shelf-pieces,—and that 
the clasp iron knees have ever been 
practised, or even proposed, by any 
other person. But all these form but 
a small part of the inventions and im- 
provements which have been brought 
forward by Sir R. Seppings, in the 
various branches of naval science. 
The spleen shown by your corres- 
eal is evident to every reader; 
ut few may be acquainted, that not- 
withstanding Sir Robert had shown 
such ability in ship-building, as well 
as in mechanical inventions, yet he did 
not arrive at his present situation of 
Surveyor of the Navy until he had 
Mr. Knowles in Defence of Sir Robert Seppings. 
39 
passed through all the gradations of 
office, nor until he had completed up- 
wards of thirty years of faithful and 
active service ; that he had every right 
to expect this situation, even if he had 
not rendered such signal services; as 
he was apprenticed, at a considerable 
expense, to a gentleman (Sir John 
Henslow) who was Surveyor of the 
Navy, and who had in bis turn been 
an apprentice to Sir Thomas Slade, 
who also filled that office. 
The last paragraph in ‘the letter 
signed “Fact” is obviously written 
with the view of conveying to the pub- 
lic, that the author of “the Precursor” 
and the writer of that letter are the 
same person; or why, it is asked 
by every reader, should the writer 
be so tender of the opinions given 
in “the Precursor?” ‘This opinion 
I cannot for a moment entertain: I 
cannot believe, that any person hold- 
ing the rank of a captain in the 
British navy, would descend to ca- 
lumniate a gentleman, who he must 
be conscious has rendered great ser- 
vices to his country, and who, from his 
general urbanity of manners, is inca- 
pable of giving offence to any one. 
Nor can I imagine, that.a person who 
has given to the public ohe work on 
naval affairs, and has sent out a pros- 
pectus of another, (by whichit appears 
he intends to trace naval improve- 
ments from the first naval architect, 
Noah, down to the present time,) 
should be so grossly ignorant of the 
progress of the science upon which he 
intends to treat. But, although indi- 
rect, it certainly behoves Capt. Lay- 
man to disavow such an imputation. 
JOHN KNOWLES. 
London ; July 11, 1822. 
— 
SUNDRY QUERIES. 
S1r,—In the well-written letter of “A 
Johnian,” which appeared in your last 
Number, allusion is made to a new mathe- 
matical calculus, which has been very ad- 
vantageously employed by several emi- 
nent foreigners ; and, as I have from time 
to time seen similar allusions made else- 
where, I am induced, through the medium 
of your extensively circulated Miscellany, 
to solicit either your above-mentioned 
correspondent, or some other of your ma- 
thematical readers, to inform me in what 
works, which may be obtained by applica~ 
tion to the regular booksellers, are the 
principles of this calculus laid down, or 
such information conveyed as will enable 
one, who may possess sufficient prelimi- 
nary knowledge, to become elite 
wi 
