Goldschmidt goniometer
Date: 1909-1920
Inventory Number: 2004-1-0338
Classification: Goniometer
Subject:
Maker: Stoe & Cie (1887-present)
Maker: Bausch & Lomb Optical Company (1853-present)
Maker: Standard Transformer Corporation (1930s-present)
Cultural Region:
Place of Origin:
Dimensions:
56 x 92 x 53 cm (22 1/16 x 36 1/4 x 20 7/8 in.)
including table: 141 x 122 x 64 cm (55 1/2 x 48 1/16 x 25 3/16 in.)
Accessories: table-mounted; embedded, modern electric lights
DescriptionA large metallic instrument on a wooden base which in turn rests on a table with wooden top and iron legs. The instrument consists of two almost-separate pieces: the goniometer proper, and the collimated light source which stands partially on a wooden cube and whose end is supported by an arm of the goniometer. In addition, the base holds a transformer that is the power source for the collimator and for two other lights that are part of the goniometer.
The goniometer is composed of an iron base with three legs (one of which continues upward to hold an end of the collimator) that holds an axis on which two concentric horizontal wheels are mounted. The larger wheel is fixed and holds the movable base of a brass telescope that uses it as a rail. The smaller brass wheel supports a horizontal bar that holds another wheel assemblage, this time with a vertical wheel. On the other side of the horizontal bar is a counterweight. The steel and brass vertical wheel assemblage supports a complex holder at its end.
Both the horizontal brass wheel and the vertical wheel have a set of eyepiece and (electric) light to determine the angle to which they are rotated very accurately.
The collimated light source is composed of a light attached to a telescope-like extension that points towards the goniometer.
The goniometer is composed of an iron base with three legs (one of which continues upward to hold an end of the collimator) that holds an axis on which two concentric horizontal wheels are mounted. The larger wheel is fixed and holds the movable base of a brass telescope that uses it as a rail. The smaller brass wheel supports a horizontal bar that holds another wheel assemblage, this time with a vertical wheel. On the other side of the horizontal bar is a counterweight. The steel and brass vertical wheel assemblage supports a complex holder at its end.
Both the horizontal brass wheel and the vertical wheel have a set of eyepiece and (electric) light to determine the angle to which they are rotated very accurately.
The collimated light source is composed of a light attached to a telescope-like extension that points towards the goniometer.
Signedon horizontal brass wheel: P. Stoe Inh. Fritz Rheinheimer / Heidelberg, Germany
on transformer: Part. no. P-3022 / Standard Transformer Corp. / Chicago, lIL
on illuminator: Bausch and Lomb
on transformer: Part. no. P-3022 / Standard Transformer Corp. / Chicago, lIL
on illuminator: Bausch and Lomb
FunctionThis is an instrument that is used to determine the angles made by adjacent crystal faces, which used to be the primary way to identify crystals up to the 1920s. It can also be used to determine the refractive index of a crystal by measuring the angles that light makes when crossing through it.
The goniometer is an assemblage that works by being able to hold and rotate a small crystal by any angle, and accurately measure these rotations. The crystal would be affixed (usually by wax) to the holder at the end of the vertical wheel system with the most prominent straight edge of the crystal pointing vertically. One would point the collimated light (which produces a narrow strip of light) at an angle of about 45 degrees to one of the faces adjacent to the vertical edge, and also point the telescope towards the same face, also about 45 degrees to it, making a right angle to the collimator such that the light would be reflected by the crystal face and be seen in the telescope as a narrow strip of light. One would write down the angles at which this occurred, and then rotate the horizontal brass wheel until the next crystal face (across the vertical edge) reflected the collimated light in exactly the same way. Writing down these new measurements and subtracting the first ones, one would get the exact angle between the two crystal faces. This process would be continued and one could even use the system to measure the angles of the other (non-vertical) crystal edges by using combinations of movements of the vertical and horizontal wheels and using more complex mathematical formulas to deduce the angles.
The eyepieces and electric lights that are mounted on the system help determine the angles as accurately as possible and were needed as the goniometer was operated in a darkened room. The light may have been originally gas or arc-based.
The goniometer is an assemblage that works by being able to hold and rotate a small crystal by any angle, and accurately measure these rotations. The crystal would be affixed (usually by wax) to the holder at the end of the vertical wheel system with the most prominent straight edge of the crystal pointing vertically. One would point the collimated light (which produces a narrow strip of light) at an angle of about 45 degrees to one of the faces adjacent to the vertical edge, and also point the telescope towards the same face, also about 45 degrees to it, making a right angle to the collimator such that the light would be reflected by the crystal face and be seen in the telescope as a narrow strip of light. One would write down the angles at which this occurred, and then rotate the horizontal brass wheel until the next crystal face (across the vertical edge) reflected the collimated light in exactly the same way. Writing down these new measurements and subtracting the first ones, one would get the exact angle between the two crystal faces. This process would be continued and one could even use the system to measure the angles of the other (non-vertical) crystal edges by using combinations of movements of the vertical and horizontal wheels and using more complex mathematical formulas to deduce the angles.
The eyepieces and electric lights that are mounted on the system help determine the angles as accurately as possible and were needed as the goniometer was operated in a darkened room. The light may have been originally gas or arc-based.
Curatorial RemarksThe goniometer is from around 1909-1920 except for the lights which probably have been replaced several times, the last of them around the 1950s.
Because it is signed with with the name of Fritz Rheinheimer, the nephew of Stoe, we know it was made after 1909.
Because it is signed with with the name of Fritz Rheinheimer, the nephew of Stoe, we know it was made after 1909.