Surveying,gunlaying,nautical or what?

I want to say it's an old surveying instrument, and in impressive condition, considering it's circumstances, but it has no apparent provision for dealing with angles... So, until you find something akin to a (royal society of the king's surveyors) museum, why not take it to a antiques auction and have it appraised, at least informally. Specifically ask about the blackening. But, for starters, how long do you think it was in that attic, and do you have any idea who might have put it there?

It seems to be a surveying instrument used in conjunction with a flat bed table. Rather accurate scaled plans could be done in the field.

It did not need horizontal degrees because the direction line was plotted straight onto the map.

The table were fitted with a leveling bubble or something. The slit in the front was also there for determining the slope to the target point and the spot height was easily calculated. By deducting the bottom reading (of the staff) from the top reading distance calculations was also possible.

When I started working we had a later version of the instrument. It was fitted with an optical dumpy. Theodolites using the same principle was also made.

I don't think it could be used at sea because the base should be kept steady.

"It seems to be a surveying instrument used in conjunction with a flat bed table. "

AKA a surveyor's plane table which had to be leveled in both directions. There is a parallel bar on the side to draw lines parallel to the line of sight. The folding bar on the left has a thin wire in the center of a vertical slot and the one on the right a thin slot to establish the line of sight with the front wire.

I am of the opinion it is of WWI vintage.

OK, I think I get it, you want to draw a line from a point in an exact direction:

you squash the parallel rulers together and place the narrow rule close to the point;

you then site the direction accurately and hold the wider rule in place,

then, move the narrow parallel rule out to the point and draw the line.

??

It is called an alidade. It was used along with a compass in "plane table" surveying; a drawing board mounted on tripod with a spirit level for levelling & a plumb line for the bench mark. The surveying was done by triangulation.

Just googled your answer, and found this..

http://www.geometricum.com/Pic_of_Month_022004.htm

It is a rudimentary alidade. It appears to be very old. The plane table and alidade were generally used for site or construction mapping. This is the first I've seen without optics. I wonder if the plane table and tripod are in the same attic.

It certainly is a good idea to go back and make a thorough search of the attic, just on general principles.

But, back to the instrument. The lack of optics is the source of my hesitation about calling it a surveying instrument. On the one hand, surveying instruments have typically incorporated optics for several hundred years now, since before the time of George Washington... However, the condition of the case is much too good to have survived, so intact, for that long.

On the other hand, an investigation of the blackening could reveal that it is from use in a chemically active environment, like say, certain mining operations... It is thusly plausible that it could have been a specialty alidade that was used to map ("topo") in existing (operating and/or abandoned) coal mines, say. Such conditions may have made it preferable to avoid frequent cleaning of the lenses from ongoing conditions of excessive and/or highly variable dustiness... But, some vertical angles would have to be measured with other equipment, thereby requiring some redundancy in such operations...

Clearly, more authoritative investigation is called for...

(also, "R. E." could be an abbreviation for "Royal Engineers", among other possibilities. "C. O." could likewise be an abbreviation for "Commanding Officer" as well. Also, the serial number could eventually lead to the actual answer, but it could be along a very circuitous path...)

Guest: Lend credence to you post by registering and declaring yourself.

Most of your post is speculation and lack of background information aka ignorance.

Such primitive or elementary instruments were used about 80/100 years ago, and earlier, before fancy optical alidades and theodolite were available. A little research and you should find that George Washington used a plane table and alidade to survey property lines. Also used by Forestry Service in Fire Towers until the use of plane and geopositioning came into use.

The Alidade Is Used To Establish Horizontal angles

The Theodolite Measures Vertical Angles Also

SURVEYING

SURVEYERS

More than most folks want to know on the subject.

Thank you for your response to my reply.

As a consequence, I won't be vacationing in Tennessee any time soon.

I agree that it is probably a surveying instrument.

You might send your description and pictures from several angles to www.pobonline.com it is a magazine for surveyors. POB stands for Point of Beginning, something every survey or record map is suspose to have.

I am a registered surveyor and Yes, it does appear to be an alidade used in plane table surveying. It may also be just a simple sighting instrument for use on a plane table over a map centered on a given location. Then by sighting along the instrument, one could give a fairly accurate bearing to a given location (such as a forest fire).

This is an instrument that was originally designed to be use in fire watch towers by an individual who resided in a fire watch tower for the summer months. A map of that particular "district" was placed on a large table mounted in the center of the room. This table was sometimes a huge cabinet system with multiple drawers and shelves to store maps that could be placed on the table, one for each cardinal direction, and there was also a table that could be taken into the forest by the "ranger" that mounted on a tripod. The map was mounted, the alidade was placed on the table, and again the reading was take.

Sometimes these towers were 40 to 80ish feet above the soil surface of an apparent mountain top. Sometimes it was protected at the bottom by the trees nearby, but, the observation area had to have an unobstructed 360 degree view of the area. The observer was to use this in conjunction with the tabletop, which had graduations in degrees and minutes, o-360, read as an azimuth. When a smoke plume was located, the "ranger" would get a siting, either use a crank phone to a local headquarters, or in later times, a two-way radio, and report the smoke siting. This would be triangulated with an adjacent tower. More than one tower used to be up on a mountaintop in the area of interest, so if I saw a smoke plume, I would call in and make the report, then call an adjacent tower and ask them for an angle as well. Between the two reports, a location was determined and smoke jumpers were dispatched to quell the fire. This was used predominately in undeveloped forests of vast size where there was no harvesting either planned, allowed or was being done in the first place. This instrument was valuable in protecting the forest lands of the Pacific Northwest for a good number of years. If you were a young person, male or female, and were looking for a summer job, didn't mind being alone for extended periods of time, and were lucky enough to get chosen for the job, it was unlike an other for that era. Often, if the smoke siting was within hiking distance, they sometimes would go to the area and make some initial suppression efforts, digging a fireline by hand, and hoping against time that smokejumpers would make it to the area before it grew too big.

How to use it. The eyepiece was the thin slit, and the other end was the objective. The wire was lined up on the smoke, and then using the scale on the table to read the degree and minute along the straight edge of the ruler. Once that data was read and passed on, the party began.

Females were often the best suited for the job as they would be most likely to not take in boredom as easily as the male. This ability made them take more interest in their surroundings and better suited for the job. During intense thunder and lightning storms the tower was often protected with suspended boards of plywood which served as shutters. These were pinned down in place and the observer departed for lower grounds. These towers were protected by lightning rods and cables that went to the ground to dissipate the intensity of the lightning strike. It was one of the most interesting jobs of the era, and most of them have been since removed from service.

By the way, the "cute little compartment for a screwdriver" was a very integral part of the tool. That screwdriver was used to re-tighten the pivot screws on each upright leg, and to also replace the siting wire on the objective site.

I have such an instrument that I picked up at a garage sale one weekend that belonged to a forest ranger here in the Northwest of Oregon. It was made in the 1904's, and is in good shape. I believe the manufacture was Kueffel and Esser, a manufacture that made surveying instruments, including drafting sets, and I believe they still might.

Good find.

Hi All,Many thanks for ,your useful and extensive information about the mystery object.It doesn't actually belong to me but to a colleague who doesn't have access to the superb brains trust of CR4,so I have been getting him to look at the answers on the site.The suggestions have all been on the same lines,but especially interesting are the examples of actual usage. We showed it to a Greek sea captain who said that his ancestors had used a similar instrument,but hadn't we got GPS in Scotland yet? Cheeky b...

We work in the docks so were going to get a chart and climb up one of our silos with a clear view of our Forth River estuary and try it out on some landmarks, islands, lighthouses etc.

There aren't any more associated objects in the attic unfortunately.

My apologies for not replying earlier but Inland Revenue requirements take up all my spare time just now,all British self employed my thoughts are with you!

Just a few additional thoughts...

The blackening is still a curious feature. If it was applied intentionally, then carefull removal may reveal a manufacture's stamp and/or unique serial number syntax, in addition to critical chemical details. If said blackening was accidentally applied, that could point to it's having been burned in a fire that consumed a fire watch tower, such as mentioned in other posts. But then, why/how was the case still in such good condition...

It is just possible that the instrument did originally have some sort of scope on it, and that the two gnurled strips on it were where said scope was (cut) off, for who-knows-what purpose, and the strips were subseqentely ground-down in order (leave/make still) usable the remaining portion of the alidade. Probably, only "R.E-CO" would know for sure...

Another aspect is that it was probably a european instrument that was used in the U.S., unless there are similar watch towers in Europe, to where it somehow returned.

If only it could speak for itself, it would probably have an interesting little story to tell...

I just reviewed the first picture of this item, and I see that it does have a small parallel bar to one side. In those that I have seen I didn't see that extra item on the ones used for forest watch applications. My latest impression could be that of maritime use, such as plotting adjacent courses.

On the mention of "blackened", the original black paint could be of a dull finish so as to induce a glare factor as it was being directed towards an evening or morning sunlight view as the user got bearings for the task. I have some magnetic compasses for land survey use and they have a nice shiny black paint finish on the housing, but on the sites the coloring is flat black.

How's the siting wire? If it's sagging, it was installed during a hot time of the year, and if it's broke, it was popped by expansion after being adjusted during a cold part of the year. It only it could talk, what stories it may tell, eh?

Thanks for your sharing this item with the "community".

Yes, it is a good observation that the parallel bar is relatively small. On parallel rules used in maritime plotting, the side bar is typically the same size as the main bar, and the significantly longer rotating arms allow a sideways motion of about three times the width of the main bar, in order to facilitate the transfer of parallel lines across a relatively large map, with fewer motions, and thusly, fewer opportunities for human error. Thus, the little bar indicates that the subject instrument was probably not intended for the transfer of parallel lines across a very large navigational map...

And so, the question remains as to what kind of a map would be appropriate for relatively small transfers of parallel lines?...

Just on the blackening,I think it was chemically blackened,as it is perfectly uniform with no thick or thin parts,and complete without any chips or bare metal anywhere.It is matte,totally non-reflective. It is so thin that there are certainly no hidden markings,microscopic tool marks could be discerned through the blackening.

The parallel action is curious as it is of only about 1cm travel,certainly not enough to transfer the azimuth to a compass rose on a chart.The finger grips on the sighting part are not duplicated on the narrow ruler so it would appear that unlike a chart parallel it is only intended to transfer the bearing laterally a small distance,and not to repeat step.When the parallel is closed there are two small alignment pins attached to the main body and registering with holes in the narrow ruler.

Down int' docks we've been rained on,snowed on and blown on,so we've not had a chance to try it up high.The owner has now reclaimed it so we'll never get to try it.

Many thanks for your considered replies and suggestions.