pocket aquatic and screw-barrel simple microscopes
Date: circa 1768
Inventory Number: 1007
Classification: Microscope
Subject:
Maker: Peter & John Dollond (fl. 1766 - 1804)
Owner: Dr. George Engelmann (1809 - 1884)
Donor: William T. Councilman (1854 - 1933)
Collector: Ernst-Lewis Collection of Microscopes
Cultural Region:
Place of Origin:
Dimensions:
18.5 x 15.8 x 13.2 cm (7 5/16 x 6 1/4 x 5 3/16 in.)
Accessories: Aquatic and Wilson attachments; 2 lenses to fit either ; 2 silverplated Lieberkuhns with lenses ; stage forceps ; tweezers ; 3 bone slides ; 1 brass framed glass slide for Wilson
Bibliography:
Directions for using the Pocket Aquatic Microscope as Improved by John Ellis, Esq. F. R. S. and made by P. and J. Dollond, Opticians to his Majesty in St. Paul's Church-Yard, London.
DescriptionAn arm to hold the optical assemblies slides in a socket on a rod that fits into the top of a round pillar. A thumb screw on the pillar sets the height of the arm above the stage or mirror. A mirror on a pin slips into a hole at the bottom of the pillar. The pillar is screwed into a socket in the top of the box.
Optical assemblies are included for two types of microscopes:
1) An Ellis aquatic-type microscope is set up by means of a brass arm into which can be screwed different objectives. The stage is a circular ring into which a watch glass fits. The stage is supported on an arm that slips over the top of the pillar.
2) A Wilson screw-barrel type microscope is fixed to a brass arm, which can be inserted into the top of the pillar.
The objectives fit either setup.
The sharkskin covered box holds 3 ivory slides and one brass slide, a stage forceps, 2 objective lenses and 2 lieberkuhns, and small forceps.
An explanation sheet was found under a tray in the box, but is no longer with the instrument. According to Dr. Lewis, it was "Directions for Using the Pocket Aquatic Microscope as Improved by John Ellis, Esq. F.R.S. and Made by P. and J. Dollond, Opticians to his Majesty; in St. Paul's Church-Yard, London." (Another copy is in the CHSI Library as lib.564.)
Another sheet in the tray includes calculations of the magnifications possible with the available lenses. This sheet was drawn up by Dr. George Englemann (1809-1884), a prior owner of the microscope, and is German.
Dr. Engelmann's sheet of calculations shows a scale sketch of a square of almost exactly 3 mm linear dimension and its appearance after magnification. He gives his estimates of these and the corresponding fields of view as follows:
a) the original without magnification
b) large lieberkuhn 7.5
c) small lieberkuhn 19.5
d) magnifier no. 3 20
e) magnifier no. 2 22.5 (missing)
f) magnifier no. 1 34
Optical assemblies are included for two types of microscopes:
1) An Ellis aquatic-type microscope is set up by means of a brass arm into which can be screwed different objectives. The stage is a circular ring into which a watch glass fits. The stage is supported on an arm that slips over the top of the pillar.
2) A Wilson screw-barrel type microscope is fixed to a brass arm, which can be inserted into the top of the pillar.
The objectives fit either setup.
The sharkskin covered box holds 3 ivory slides and one brass slide, a stage forceps, 2 objective lenses and 2 lieberkuhns, and small forceps.
An explanation sheet was found under a tray in the box, but is no longer with the instrument. According to Dr. Lewis, it was "Directions for Using the Pocket Aquatic Microscope as Improved by John Ellis, Esq. F.R.S. and Made by P. and J. Dollond, Opticians to his Majesty; in St. Paul's Church-Yard, London." (Another copy is in the CHSI Library as lib.564.)
Another sheet in the tray includes calculations of the magnifications possible with the available lenses. This sheet was drawn up by Dr. George Englemann (1809-1884), a prior owner of the microscope, and is German.
Dr. Engelmann's sheet of calculations shows a scale sketch of a square of almost exactly 3 mm linear dimension and its appearance after magnification. He gives his estimates of these and the corresponding fields of view as follows:
a) the original without magnification
b) large lieberkuhn 7.5
c) small lieberkuhn 19.5
d) magnifier no. 3 20
e) magnifier no. 2 22.5 (missing)
f) magnifier no. 1 34
In Collection(s)
Signedengraved on stage: Dollond London
on instruction sheet (now missing): MADE BY / P. and J. DOLLOND, OPTICIANS to his MAJESTY; / IN ST. PAUL'S Church-Yard, LONDON.
on instruction sheet (now missing): MADE BY / P. and J. DOLLOND, OPTICIANS to his MAJESTY; / IN ST. PAUL'S Church-Yard, LONDON.
Historical AttributesPrice on handbill advertising and giving directions for this microscope kit is £3.13.6.
The microscope was owned by a physician and botanist, Dr. George Engelmann of St. Louis, Missouri. Englemann was the founder of the first American botanical garden. He used the microscope in the 1840s for his pioneering descriptions of Western flora and cacti. To obtain the accurate measurements that he needed to identify species, Englemann calculated each lens's magnification on a handwritten note still inside the case. Englemann corresponded with Harvard's Asa Gray about how to run the Missouri Botanical Garden.
The microscope was owned by a physician and botanist, Dr. George Engelmann of St. Louis, Missouri. Englemann was the founder of the first American botanical garden. He used the microscope in the 1840s for his pioneering descriptions of Western flora and cacti. To obtain the accurate measurements that he needed to identify species, Englemann calculated each lens's magnification on a handwritten note still inside the case. Englemann corresponded with Harvard's Asa Gray about how to run the Missouri Botanical Garden.
Primary SourcesDirections for using the Pocket Aquatic Microscope as Improved by John Ellis, Esq. F. R. S. and made by P. and J. Dollond, Opticians to his Majesty in St. Paul's Church-Yard, London (London, [1766?]). In CHSI library as lib.564.
ProvenanceDr. George Engelmann, St. Louis; whereabouts unknown; obtained from Dr. George Clark by Dr. W. T. Councelman, and presented to Dr. Ernst in 1908; Ernst-Lewis Collection of Microscopes (inv. no. 7), Harvard Medical School.