MD design dates back 400 years

[TerryC]

Bought two metal detectors on E-Bay today. The design dates back over 400 years. Anyone figure out what I bought? I'll tell you soon, don't jump off that bridge just yet. TTC

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[63bkpkr]

dowsing rods? magnets? a very old Whites??........63bkpkr

[strickman]

spanish dip needle?

[TerryC]

SHARP, Strick! Get it? Needle... sharp? There were two so I bought both. They work, I presume, by finding the magnetite sand... black sand... many times located with the gold deposits in streams. One was for 40 and the other for 120. The spanish of mexico used them in the southwest. Now, we know they had vast silver and gold holdings back then, so maybe they work. I'll find out. Will take some pics when they get here. Tnx, Strick and 63. TTC

[Oakview2]

Hey Terry, can you post a picture.

[woof!]

There are two kinds of things called "Spanish needles".

Type #1 is two slender metal rods held in the hands and used for dowsing. My grandfather used them and everyone but him noticed that he couldn't locate diddlysquat with them. Your results may differ, but if you can't tell the difference between success and failure you could wind up like my grandfather.

Type #2 is a primitive geophysical magnetometer comprising a compass suspended in the vertical plane indicating magnetic dip angle. A regular compass can also be used as a geophysical magnetometer but that kind of use requires a long line of sight, impossible in most mines and in many types of aboveground terrain. The dip compass uses gravity (which is always vertical) as the reference, allowing the dip compass to be used (for instance) inside mines.

--Dave J.

[Terry Soloman]

Way cool!

[TerryC]

Oak, when they arrive, I will post pics. Nice pics, Terry. Now, to the Woof! Dave, We can exclude type #1. My needles are of the type#2, as described. I must declare that your deffinition as wrong. Dip needles do not measure gravity but the earth's magnetosphere (magnetic flux) relative to the horizon (level). Regular compasses (map and compass are my PASSION) cannot be tilted on side (maybe you said this as a metaphore) as the jeweled point will then not support the hanging needle. A relatively new form of mag compass DOES dip with the earth's magnetic field, making it a "dip needle" in a sense. It is sold as a GLOBAL compass as it has the height in the compass "chamber" to follow the earth's lines of flux on the most heavily populated portions of the earth WHEN IT IS HELD LEVEL. They, also will not work tilted. Your reference to a "dip compass" would not be a true dip needle as it has no magnetic uses. The following are Wikipedia's results to SPANISH dip Needles. They had no results for the three words Spanish Dip Needle or dip needle (lengthy but very relevent): A magnetometer is a measuring instrument used to measure the strength or direction of magnetic fields
Magnetometers are distinct from metal detectors, which detect metallic objects by detecting their conductivity. Magnetometers can detect only magnetic (ferrous) metals, but can detect such metals at a much larger depth than a metal detector; magnetometers are capable of detecting large objects, such as cars, at tens of meters

Dip circles
are used to measure the angle between the horizon and the Earth's magnetic field (the dip angle). They were used in surveying, mining and prospecting as well as for the demonstration and study of magnetism. Tnx for your response. TTC

[strickman]

Terry ,here's a link to a thread on dip needles http://www.treasurenet.com/forums/do...s-compass.html

[TerryC]

Terry ,here's a link to a thread on dip needles http://www.treasurenet.com/forums/do...s-compass.html

Tnx, Strick. I checked out the thread. The pic OldBillinUT is exactly what I bought times two. Although the one shown is exact, the "cheaper" one looked to have aluminum inside instead of brass. Tnx lots for the reference (I read it back then) UPDATE: Here is the pic I am refering to. EXACTLY like one of the dip needles I bought. TTC

[woof!]

The one pictured is suspended in the vertical plane by a swivel on a ring, but most I've seen pictured were suspended on a chain. Both kinds are dip angle magnetometers which refer dip angle to vertical, the vertical axis being established by the suspension mechanism.

In order to measure dip angle accurately, the dip compass has to be able to rotate about the vertical axis. In principle magnetic forces could orient the plane of the dip compass magnetic north and south, but I suspect that friction is too great to achieve that, and manual rotation to find the greatest dip angle is necessary to get accurate measurements.

--Dave J.

EDIT: Dip angle is reported relative to horizontal, although the suspension mechanism itself knows nothing about horizontal, but only vertical. The indicator scale is graduated to indicate 90 degrees when the compass needle is oriented vertically (as at the magnetic north pole), and to indicate 0 degrees with a horizontal needle orientation (as at the magnetic equator).

[TerryC]

The one pictured is suspended in the vertical plane by a swivel on a ring, but most I've seen pictured were suspended on a chain. Both kinds are dip angle magnetometers which refer dip angle to vertical, the vertical axis being established by the suspension mechanism.

In order to measure dip angle accurately, the dip compass has to be able to rotate about the vertical axis. In principle magnetic forces could orient the plane of the dip compass magnetic north and south, but I suspect that friction is too great to achieve that, and manual rotation to find the greatest dip angle is necessary to get accurate measurements.

--Dave J.

EDIT: Dip angle is reported relative to horizontal, although the suspension mechanism itself knows nothing about horizontal, but only vertical. The indicator scale is graduated to indicate 90 degrees when the compass needle is oriented vertically (as at the magnetic north pole), and to indicate 0 degrees with a horizontal needle orientation (as at the magnetic equator).

You nailed it, Woof!(!). The only portion of a previous post that I would like to clarify is your dip compass. It had nothing to do with magnetic flux but DID use gravity as you mentioned. The dip compass you talk of was (is) needed underground to determine the horizontal so that diggins and beam construction would be plumb. Very important! Tnx for your input, Woof! TTC