306 Method of tracing Oval Arches. 
Eleven Centres. (Fig. 6.) 
AB= 9 nmm= 2.187 
AF=45 ul= 0.762 
Am=15 = -3:798 
mu. 1 ss 2.778 
=e rh= 3.488 
ts= 3 Ag= 3.765 
+= 4 AFr= 6° 20’ 25” 
A= 5° rgs= 7 41 45 
Fr=45.277 spt= 9 55 36 
gr=28.98 tou=13 54 44 
gs=29.69 unm=21 9 40 
ps=15.90 ArF=83 39 35 
pt=16.88 AsE=75 57 50 
ot= 6.568 AiD=66 2 14 
ou= 7.604 Aul=57 "7 50 
nu= 1.425 AmB=30 57 50 
* x * 
Ina letter from Mr. Miller accompanying the above communica- 
tion, and dated April 7th, 1832, it is suggested by him that it would 
be very important to the country if practical men would make known 
through a Journal of Science, “ such things, as in the course of 
their experience they judge may be especially useful to their profes- 
sional brethren,” while every thing that is erroneous or useless 
should be of course rejected. Mr. Miller goes on to remark: “ Civ- 
il Engineering is now becoming, from the numerous public works in 
the United States, a distinct and important profession. It is one in 
which a large amount both of science and experience is required 
and in which the members are able to assist each other greatly, by 
making known the results of their labors. In England this object 
is attained by an “Institution of Civil Engineers,” which however 
desirable, is hardly to be expected in a country like our own where 
they are so widely scattered. 
I have taken the liberty of asking your attention to this subject, as 
I believe that a public call would bring out a large portion of the tal- 
ent and experience of our profession. 
The enclosed paper on Oval Arches was drawn up by myself for 
my own convenience and is copied nearly verbatim from my common 
place book. I know of no work which gives a satisfactory view of 
the subject ; and am sure that the {general calculations have never 
before been published. They were made some years ago with 
much care and their accuracy has been repeatedly tested by experi- 
