English, c.1897, engraved to the objective 'POWELL & LEALAND No.114, 1/12 Apochromatic oil immersion N.A. 1.43' in a can engraved the same, objective with correction collar, in a box marked 'Power& Lealand 1/12" N.A. 1.43 Apochromatic Objective, Made in 1897 for Dr. Edmund Spitta and used by him for the 'Atlas of Bacteriology' 1898' along with a typed letter by Brian Davidson dated 7.11.73 which reads:
B.M.Davidson. 7.11.73
I have in my possession, a most interesting and historic objective. Itt is a Powell and Lealand 1/12" Apochromat, oil immersion objective, No. 114. N.A. 1.43 T.L. 250 mm. made 1897 for Dr. Edmund J. Spitta.
Initially I thought that this was just another fine objective from the hands of Thomas Powell, inspite of the details of ownership etc. in the lid of the case. However, I was reading through a profusely illustrated book by Spitta, called "Photomicrography ", printed in 1899, when I came across a reference to it in the section on High power work, Page 135. This said that for
bacteriological photomicrography, P & L had made a specially computed 1/12 N.A. 1.43 which was excellent, and principally used for the illustrations for "The Atlas of Bacteriology " by Spitta, printed in 1898.
With a certain amount of persistence and luck, I found a copy of this work, with its 111 photomicrographs of bacteria, and the reference that " most of the photographs of high magnification were taken with a P & L apochromat 1/12, N.A. 1.43, specially made for the photography of bacteria. It possesses a very flat field without loss of central definition...."
Subsequent examination by P.K.S. revealed that the back lens is asperical, figured by Powell to flattern the sperical aberation found in apochromats, but retaining the definition which is their other characteristic. In this he has been surprisingly successful and the flatness of the field is far superior to any apo. previously made, whilst the definition has not suffered, as can scan be seen in the illustrations of bacteria, showing the very delicate flagella.
This objective pre-dates by half a century or so, the successful efforts of Burch and the Russians, to produce a plan apo, and is another example of the outstanding ability of the top English makers of the 19th century.
inside the objective case is a label which reads 'This is the actual objrctive computed for and used by the late Dr. E J Spitta, especially for the photomicrographs to "Atlas of Bacteriology"
English, c.1897, engraved to the objective 'POWELL & LEALAND No.114, 1/12 Apochromatic oil immersion N.A. 1.43' in a can engraved the same, objective with correction collar, in a box marked 'Power& Lealand 1/12" N.A. 1.43 Apochromatic Objective, Made in 1897 for Dr. Edmund Spitta and used by him for the 'Atlas of Bacteriology' 1898' along with a typed letter by Brian Davidson dated 7.11.73 which reads:
B.M.Davidson. 7.11.73
I have in my possession, a most interesting and historic objective. Itt is a Powell and Lealand 1/12" Apochromat, oil immersion objective, No. 114. N.A. 1.43 T.L. 250 mm. made 1897 for Dr. Edmund J. Spitta.
Initially I thought that this was just another fine objective from the hands of Thomas Powell, inspite of the details of ownership etc. in the lid of the case. However, I was reading through a profusely illustrated book by Spitta, called "Photomicrography ", printed in 1899, when I came across a reference to it in the section on High power work, Page 135. This said that for
bacteriological photomicrography, P & L had made a specially computed 1/12 N.A. 1.43 which was excellent, and principally used for the illustrations for "The Atlas of Bacteriology " by Spitta, printed in 1898.
With a certain amount of persistence and luck, I found a copy of this work, with its 111 photomicrographs of bacteria, and the reference that " most of the photographs of high magnification were taken with a P & L apochromat 1/12, N.A. 1.43, specially made for the photography of bacteria. It possesses a very flat field without loss of central definition...."
Subsequent examination by P.K.S. revealed that the back lens is asperical, figured by Powell to flattern the sperical aberation found in apochromats, but retaining the definition which is their other characteristic. In this he has been surprisingly successful and the flatness of the field is far superior to any apo. previously made, whilst the definition has not suffered, as can scan be seen in the illustrations of bacteria, showing the very delicate flagella.
This objective pre-dates by half a century or so, the successful efforts of Burch and the Russians, to produce a plan apo, and is another example of the outstanding ability of the top English makers of the 19th century.
inside the objective case is a label which reads 'This is the actual objrctive computed for and used by the late Dr. E J Spitta, especially for the photomicrographs to "Atlas of Bacteriology"
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