photographic map of the solar spectrum
Date: circa 1888
Inventory Number: 1997-1-1675
Classification: Photograph
Subject:
Maker: Henry A. Rowland (1848 - 1901)
Cultural Region:
Place of Origin:
Dimensions:
plate 1: 27.4 x 90.1 x 0.1 cm (10 13/16 x 35 1/2 x 1/16 in.)
pate 2: 28 x 90 x 0.1 cm (11 x 35 7/16 x 1/16 in.)
plate 3: 28 x 89.2 x 0.1 cm (11 x 35 1/8 x 1/16 in.)
plate 4: 27.8 x 90.5 x 0.1 cm (10 15/16 x 35 5/8 x 1/16 in.)
plate 5: 28.1 x 90.2 x 0.1 cm (11 1/16 x 35 1/2 x 1/16 in.)
set rolled: 28.5 x 7 x 7 cm (11 1/4 x 2 3/4 x 2 3/4 in.)
DescriptionThis is a set of five photographic prints mounted on linen fabric. Each shows a black-and-white photograph of two or three portions of the solar spectrum printed one above the other. Wavelengths of light are marked in Angstroms on a scale running adjacent to each spectrum. Each negative was signed between the tracks of spectra in italics, "PHOTOGRAPHIC MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND, JOHNS HOPKINS UNIVERSITY." (Exceptions are noted below.)
The plates are each approximately 28 x 90 cm, but they have been stored rolled up.
Plate 1
This has a triple track of spectra. The range of wavelenghts are:
3080-3330
3280-3530
3480-3730
The signature is in a Roman font, with a period at the end. It is written in a different hand that the signatures on the other plates. On the reverse of the plate, "Do Not Use" is marked in pencil and underlined. Also marked on the reverse, "PHOTOGRAPHIC / MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND / JOHNS HOPKINS UNIVERSITY."
Plate 2
This has a double track of spectra. Wavelengths are:
3680-3930
3890-4130
Plate 3
This has a double track of spectra. Wavelengths are:
4080-4330
4280-4530
There is a white blemish in the shape of an arc on the left side of the plate, as if the glass-plate negative had been shattered. There are also white and black spots.
Plate 4
This has a double track of spectra. Wavelengths are:
4490-4730
4690-4940
There is a blemish consisting of three arcs on the left side, as if from a shattered glass-plate negative.
Plate 5
This has a double track of spectra. Wavelengths are:
4880-5120
5080-5320
The numerals 49, 50, 51, 52, and 53 on the wavelength scale show that a correction was made to the negative before printing.
The plates are each approximately 28 x 90 cm, but they have been stored rolled up.
Plate 1
This has a triple track of spectra. The range of wavelenghts are:
3080-3330
3280-3530
3480-3730
The signature is in a Roman font, with a period at the end. It is written in a different hand that the signatures on the other plates. On the reverse of the plate, "Do Not Use" is marked in pencil and underlined. Also marked on the reverse, "PHOTOGRAPHIC / MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND / JOHNS HOPKINS UNIVERSITY."
Plate 2
This has a double track of spectra. Wavelengths are:
3680-3930
3890-4130
Plate 3
This has a double track of spectra. Wavelengths are:
4080-4330
4280-4530
There is a white blemish in the shape of an arc on the left side of the plate, as if the glass-plate negative had been shattered. There are also white and black spots.
Plate 4
This has a double track of spectra. Wavelengths are:
4490-4730
4690-4940
There is a blemish consisting of three arcs on the left side, as if from a shattered glass-plate negative.
Plate 5
This has a double track of spectra. Wavelengths are:
4880-5120
5080-5320
The numerals 49, 50, 51, 52, and 53 on the wavelength scale show that a correction was made to the negative before printing.
Signedon each plate: MADE BY PROF. H. A. ROWLAND, JOHNS HOPKINS UNIVERSITY
Inscribedon each plate: PHOTOGRAPHIC MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND, JOHNS HOPKINS UNIVERSITY
in pencil on reverse of plate 1: PHOTOGRAPHIC / MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND / JOHNS HOPKINS UNIVERSITY
in pencil on reverse of plate 1: PHOTOGRAPHIC / MAP OF THE SOLAR SPECTRUM / MADE BY PROF. H. A. ROWLAND / JOHNS HOPKINS UNIVERSITY
FunctionThis series of photographs of the solar spectrum were made in the Physical Laboratory of Johns Hopkins University using diffraction gratings ruled by Henry Augustus Rowland. The photographs served as references for physicists and astronomers.
Historical AttributesThis series of photographs of the solar spectrum were made in the Physical Laboratory of Johns Hopkins University using a concave diffraction grating ruled by Henry Augustus Rowland on his famous ruling engine. The method of making the map was known as the Rowland method, and was based on a property of concave gratings discovered by Rowland. The property was that spectrum, as photographed in any given order, was normal and of the same scale throughout. Therefore one did not need to adjust the focus, and could just move the instrument to the part of the spectrum wanted and take the photograph on a glass plate. The negatives were enlarged and measured from one standard line to another by means of a dividing engine. The negatives were then clamped to a scale on another glass plate using the standards as reference.
Rowland made hundreds of photographs using many different gratings, but ultimately selected a few gratings as standard for the work. The laboratory sold photographs of sections of the spectrum in sets and as single sheets. A set of ten plates cost $20, and an single plate, $2.50 in 1894.
Rowland made hundreds of photographs using many different gratings, but ultimately selected a few gratings as standard for the work. The laboratory sold photographs of sections of the spectrum in sets and as single sheets. A set of ten plates cost $20, and an single plate, $2.50 in 1894.
Primary Sources"Photographic Map of the Normal Solar Spectrum [Made by Professor H. A. Rowland]," Astronomical Society of the Pacific 6 (1894): 55-57.
