More Info On Monuments

[tossedsalad]

There are two monuments in front of City Hall here in Frederick, MD that were placed a very long time ago. They are roughly aligned to the magnetic north south line. They are listed in GC.com benchmarks, but not much info is available. I would like to get info on who placed them and why along with any info on the times and their use since they were placed. This is in support of a cache I am setting up.

 

I have done a google search on about every way I can think to describe this. Are there any specific sources of info on benchmarks such as these?

[+Black Dog Trackers]

tossedsalad -

 

Some people are quite knowledgeable on such things here. However, they will all need to know more about the benchmarks you're talking about, since benchmarks in the database are installed by more than a hundred different government entities. What are the PIDs (like HV2230) of these benchamarks you want researched?

[ArtMan]

The two marks are NORTH MAGNETIC (JV2529) and SOUTH MAGNETIC (JV2528), located on the lawn in front of Frederick, MD, City Hall.

 

They are granite posts with a copper pin set within.

 

Monumentation dates for both are listed as "unknown," but my uninformed guess would be that these markers may date from construction of the city hall building in 1862. (It was the county courthouse for more than a century before being sold to the city about two decades ago. Frederick website)

 

If you want to investigate these marks in more depth, you might want to try the city or county engineering office, or possibly the local historical society. And if you do, tossedsalad, please post what your disover.

 

-ArtMan-

[+jwahl]

My first guess is that they may be marking a true meridian.

 

Many county and state governments had a practice in the 1800's of setting two points on a true meridian in local areas for the use of surveyors to set their magnetic surveying compass by.

 

The meridian would have been determined by fairly simple astronomic methods such as polaris observations. Then any surveyor can come by with his compass, set it up on the south mark, sight the north mark and adjust his declination so that the compass indicates north.

 

This would allow all surveys in the general area to be on the same basis of bearing and be very close to being on the true meridian. There are still many statutes on the books requiring these to be established locally in several eastern states.

 

I have not researched this set of marks to know if this is a possibility. If they do truly fall exactly north and south of each other and without any other knowledge the possibility seems high.

 

- jerry

 

PS I found a specific reference to what are probably these marks in the online archives of the Maryland Geological Society, Volume 1, 1897.

 

MARYLAND GEOLOGICAL SURVEY 509

 

The purposes of such lines are:

 

(a) To enable the surveyor to readily determine himself at any

time the declination or the " variation of the compass " at the county-

seat and thus to provide the means for determining the amount of

secular change.

 

( To furnish a common line whose magnetic bearing as well as

its true one has been accurately determined, on which surveyors can

from time to time test and compare their compasses.

 

If such lines had been established long ago at the various county-

seats the re-running of old lines would have been greatly simplified;

for in addition to the secular change being now accurately determin-

able, the condition of the compass used in the early survey would

have been known. The law provides, namely, that every surveyor

shall duly file with the county clerk the " amount of variation " or

magnetic bearing given by his instrument on the authoritatively

established county meridian. It is well known that compasses may

differ greatly from each other by reason of the fact that the proper

care is not, in general, bestowed on them. A magnetic needle poised

on a fine pivot point is a delicate instrument and must be carefully

handled if it is to settle in the right place when it comes to rest.

 

Nine counties have thus far availed themselves of the privilege of

having their meridian lines established in connection with the mag-

netic survey. These counties are: Baltimore, Dorchester, Charles,

Frederick, Harford, Kent, Queen Anne's, Talbot and Wicomico.

 

The method used in the establishment of the lines was that of

altazimuth observations on the sun before and after noon. When

for some reason, which only occurred once, observations could not

be made on both sides of noon, then special observations for a suffi-

ciently accurate determination of the latitude were made. The accu-

racy aimed at was, that the established line should be correct within

one minute of are. The instruments employed were those used in the

magnetic survey.

 

The line was permanently marked by two granite monuments about

four feet long and seven by seven inches square. The monuments

were generally imbedded in several courses of concrete and were

allowed to project about 5 inches above the surface. In the centre of

each was leaded, flush with the top, a brass dowel one inch in diameter

and three inches long. The line was marked by crosses cut in the

brass dowels. The tops of the monuments contained some suitable

lettering, as for example:

 

North Monument or Meridian, 1807.

 

Owing to the lay and character of the grounds about the court-

houses1 it was not always possible to plant the monuments on a true

north and south line. Of course any line whose true bearing is

known will suffice for the surveyor's purpose. It was my endeavor,

however, always to select as simple a line as possible. Thus at Fred-

erick (Frederick), Salisbury (Wicomico), Towson (Baltimore) and

La Plata (Charles) north and south lines were given; at Bel Air (Har-

ford) and Chestertown (Kent), northeast and southwest lines; at Cam-

bridge (Dorchester), a northwest and southeast line; at Centreville

(Queen Anne's), an east-southeast and west-northwest line, and at

Easton (Talbot), an east and west line.

 

After the line was established careful determinations of the mag-

netic declination, or variation of the compass, were made by me over

the monuments with the Coast and Geodetic Survey magnetometer.

The surveyor, hence, in addition to obtaining a line whose true bear-

ing was known, also had the privilege of having determined for him

the magnetic bearing with an instrument especially adapted for the

purpose. This accurate magnetic bearing gave him the means of

determining the reliability of his own instrument and of obtaining

the correction to be applied.

 

When the conditions were such that it was not possible to get

 

1 The law prescribes that the line shall be established on some public

lot adjacent to the Court House.

 

entirely beyond the disturbing influence of some artificial cause near

the place where by law the line had to be established, special mag-

netic observations were made at some point near the town where

there was no reason to suspect a local disturbance and the result of

these observations likewise furnished to the county commissioners.

 

The Frederick and Wicomico lines were established in the fall of

1896 and the remainder in the spring of the present year. More

detailed reports of each line have been prepared and sent to the

respective county commissioners and will, doubtless, be published

in some other connection.

 

Numerous inquiries have been received by the Maryland Geological

Survey with regard to simple methods for the determination of true

meridian lines—such methods as could be employed with the average

instrumental equipment of the surveyor.

 

In the hope that the furnishing of this information to the surveyor

will be instrumental in inducing him to determine the magnetic de-

clination or " variation of the compass " more frequently than is his-

custom, I take pleasure in complying with the requests for this infor-

mation .and have accordingly added the following article.

 

The method used in the magnetic survey—that of determining

the true bearing of some distant mark by solar observations—while

more expeditious for the work of the survey is not one that the

surveyor in general can employ with success. I have therefore

omitted an explanation of this method.

 

The extensive article goes on to describe in technical detail how to determine true meridian using polaris and is a common method from the 18th and 19th centuries to do so.

 

The whole article

 

How do you like that? jlw

Edited July 17, 2005 by jwahl

[tossedsalad]

Wow! This was a lot more than I expected. Thanks a lot for the info and the link.

 

If I want more info, I will contact the county commissioners. I wouldn't mind having info on non-technical aspects of these monuments (political, social...) such as who paid, who decided where it would go, what issues were involved. In short, anything about it that might be interesting. Perhaps the newspaper archives would have something. I'll have to see if the local paper was around then.

[+Neweyess]

PFF and I have visited and collected a decent size list of a number of similar monuments at courthouses in North Carolina. They were placed between 1897 and 1900. Here is just one of a number of examples: CLAY COUNTY SOUTH MERIDIAN. Typically, they are square stone monuments with a chiseled X on the top and then NCGS and USGS plus the year also chiseled on it.

Edited July 23, 2005 by Neweyess