Questions on MY0449

[+elvis3068]

Looking to expand my background knowledge with a few questions.

 

I was in downtown Nashua, NH for the first time this weekend. I came across a Civil War Monument and thought (correctly) that there would be a benchmark (MY0449).

 

http://bloomsburgasd.schoolwires.com/62822...47/IMG_7130.JPG

 

http://bloomsburgasd.schoolwires.com/62822...47/IMG_7136.JPG

 

I have a few questions for those of you more in the know than I:

 

1.) Should this benchmark be considered destroyed due to the obvious damage?

 

The mark is flat and not bronze.

 

2.) What kind of metal did USGS use for their benchmarks (probably) prior to the 20th century?

 

3.) About what time did the benchmarks change from being flat?

 

Thanks for any info/insight you can give. I do enjoy reading this forum often.

Edited October 18, 2010 by elvis3068

[AZcachemeister]

It appears (can't really see 'obvious damage' in tiny picture) that the 'Datum Point' (the dot at the center of the cross-hairs' is still OK. The disk can take quite a beating and still be considered OK.

[mloser]

1. I looked at other pics of the disk and agree... the datum point is visible and in good shape. I am not even sure I would report this as poor condition. It is completely usable.

 

2. The mark probably IS bronze, no matter what it seems to be. I don't think they ever used any other metal. The patina on disks can make them look like everything from gold to steel. Some even get a green patina like copper roofs.

 

3. There are some threads here about flat vs rounded disks. If I recall correctly there were only a few years of flat disks around the turn of the 20th century--1899-1905ish. Someone who retains this sort of thing will chime in soon I bet!

[Bill93]

GC log page MY0779 has some larger pictures also. See Cache Test Dummies.

 

Agreed, the datum point is probably undisturbed unless the whole disk is loose. "Position good, but part of disk is missing"

 

While George has written a good paper on C&GS disks, I don't think I've seen much on USGS marker history.

 

What metal did you think it was? I'd have taken it for bronze after looking at all the logged photos. Bronze comes with many minor variations in its alloy formula and reacts many ways with the various environments it is in to produce various colors. Aluminum was sometimes used, also.

[+elvis3068]

.

 

What metal did you think it was?

 

I'm a chemist, so I'm used to looking at matter critically. I thought it was either aluminum or a nickel alloy. It did not have that bronze "tinge." If the USGS HAD used aluminum, I would think that would be a possibility. Aluminum oxide is white and there was some traces of that on the marker.

[Papa-Bear-NYC]

....

What metal did you think it was?

...

I'm a chemist, so I'm used to looking at matter critically. I thought it was either aluminum or a nickel alloy. It did not have that bronze "tinge." If the USGS HAD used aluminum, I would think that would be a possibility. Aluminum oxide is white and there was some traces of that on the marker.

 

USGS certainly did use aluminum in early disks going back to around 1900. Search for some threads and you'll find a few discussions of this. Here's one I recovered (circa 1900) that is both flat and aluminum.

 

PE0518

 

Edited October 18, 2010 by Papa-Bear-NYC

[mloser]

Papa -Bear is right (as usual). There are aluminum disks. I have seen reference to them in descriptions as being aluminum and have seen them with my very own eyes. They seem to be circa 1900 as PB mentioned.

 

I have searched for some of my local marks based on Primary Leveling books that I found on Google Books and some mention aluminum markers. I just looked at one book and it lists both bronze and aluminum markers from what appears to be the same level line and date in 1900. I am not sure what this means. Maybe they were switching from aluminum to bronze and had old disks left to use.

 

Fogelsville, German Reformed Church; aluminum tablet set in southwest corner of foundation

wall under corner stone, stamped "514 HARRISBURG 1900"

 

New Tripoli, 0.5 mile northeast of; bronze tablet set in in southeast corner of stone basement

of barn owned by A. Bennikoff, stamped " 573 HARRISBURG 1900 "

[+elvis3068]

....

What metal did you think it was?

...

I'm a chemist, so I'm used to looking at matter critically. I thought it was either aluminum or a nickel alloy. It did not have that bronze "tinge." If the USGS HAD used aluminum, I would think that would be a possibility. Aluminum oxide is white and there was some traces of that on the marker.

 

USGS certainly did use aluminum in early disks going back to around 1900. Search for some threads and you'll find a few discussions of this. Here's one I recovered (circa 1900) that is both flat and aluminum.

 

PE0518

 

 

That certainly is a very similar disk to the one we saw in Nashua. I would be very confident to say that it was aluminum at this point. Thanks so much!!