A Stanhope lens is a simple, one-piece

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...

invented by Charles, the third Earl of Stanhope. It is a

cylinder A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infin ...

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of ...

with each end curved outwards, one being more

convex Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytope ...

than the other. The focal length of the apparatus is at or within the device so that objects to be studied are placed close to or in contact with the less curved end. Because its construction is simple and economical, it was popular in the 19th century. It was useful in

medical practice Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care practic ...

for examining

transparent Transparency, transparence or transparent most often refer to: * Transparency (optics), the physical property of allowing the transmission of light through a material They may also refer to: Literal uses * Transparency (photography), a still, ...

materials such as

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s and

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...

René Dagron René Prudent Patrice Dagron (17 March 1817 – 13 June 1900) was a French people, French photographer and inventor. He was born in Aillières-Beauvoir, Sarthe, France.

modified the lens by keeping one curved end to

refract In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

light while sectioning the other end flat and locating it at the

focal plane In Gaussian optics, the cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system. These are the '' focal points'', the principal points, and the nodal points. For ''ideal'' ...

of the curved side.The Strad
Dagron used the modified Stanhope lens in mounting his microscopic pictures in photographic jewels known as Stanhopes. A rival lens is the

Coddington magnifier A Coddington magnifier is a magnifying glass consisting of a single very thick lens with a central deep groove diaphragm at the '' equator'', thus limiting the rays to those close to the axis, which minimizes spherical aberration. This allows for ...

. This was considered superior as a magnifier but was more expensive.

References

americanhistory.si.edu
Magnifiers Microscopes {{optics-stub