the lens-plates 47.07mm x 27.6mm x 1.56mm with 3 rivets and hammer marks around lens aperture, with spherical lens, the long-screw adjuster with flattened handle, the shaped bridge-piece with vertical adjustment screw and focusing screw, with angle bracket and securing screw, good uniform patination, in a card case marked 'PERSONAL PROPERTY OF B. BRACEGIRDLE'

Antonie van Leeuwenhoek (1632–1723), was a Dutch scientist and tradesman widely regarded as the "father of microbiology." His groundbreaking work with microscopes enabled him to explore a previously invisible world, revolutionizing the fields of biology and microbiology. Van Leeuwenhoek's life and scientific contributions were marked by curiosity, keen observational skills, and a commitment to scientific inquiry that led to some of the most significant discoveries in natural history.

Born in Delft, Netherlands, Van Leeuwenhoek initially pursued a career in textile commerce. He worked as a draper, a profession that involved the inspection of cloth quality. His interest in lenses and magnification arose from his need to observe the threads of textiles more closely, a practice common in the industry.

Van Leeuwenhoek’s advancements in microscopy were not the result of formal scientific training but rather the outcome of self-taught experimentation and dedication. While simple magnifying glasses had been in use for centuries, Van Leeuwenhoek’s microscopes were far more advanced. He did not invent the microscope, as early forms had been created by figures like Zacharias Janssen and Galileo Galilei. Instead, Van Leeuwenhoek’s unique contribution lay in his ability to improve the quality of lenses, enabling far greater magnification.

Using small lenses, Van Leeuwenhoek built simple single-lens microscopes that could magnify objects up to 275 times, an unprecedented level at the time. His methods produced lenses of superior quality, allowing him to observe objects in finer detail than any other scientist of his era.

Through his microscopic investigations, Van Leeuwenhoek became the first person to document and describe the existence of microorganisms, which he referred to as "animalcules." His observations included bacteria, protists, sperm cells, and red blood cells. In 1674, he reported his discovery of single-celled organisms living in water, and in subsequent years, he provided detailed descriptions of various forms of life, such as protozoa and algae.

Van Leeuwenhoek’s observations of bacteria in dental plaque and other substances were particularly groundbreaking. His detailed descriptions of the minute organisms helped establish the foundation for microbiology. He meticulously recorded his findings in correspondence with the Royal Society of London, where his work was met with both skepticism and admiration.

The impact of Van Leeuwenhoek’s work cannot be overstated. His discoveries transformed scientific understanding of life at a microscopic level and challenged prevailing notions of biology. Until his work, the existence of a microbial world was entirely unknown. His findings laid the groundwork for future scientists, such as Louis Pasteur and Robert Koch, whose work on germ theory and microbiology expanded upon Van Leeuwenhoek’s early observations.

Although Van Leeuwenhoek did not publish formal scientific papers, he communicated his findings extensively through letters to the Royal Society, which translated and published them in *Philosophical Transactions*. His documentation and sketches of microorganisms were essential for validating his discoveries and spreading his influence across Europe. Additionally, his improvements to lens-making influenced the design of microscopes in subsequent centuries, establishing standards that would be refined in later technological advancements.

Van Leeuwenhoek's contributions to science were widely recognized during his lifetime, and he continued his work well into old age. He was visited by notable figures such as Peter the Great of Russia, who was intrigued by his research. Despite his lack of formal education, Van Leeuwenhoek was elected a Fellow of the Royal Society in 1680.

Brian Bracegirdle (1933–2019) was a well known figure in the fields of microscopy and the history of scientific instruments. His career began in the study of biology, where he earned a PhD in fungal spore dispersal from the University of London. However, his interests soon expanded into the history and development of microscopy, leading him to become a leading expert in the field. Bracegirdle had a long-standing association with the Science Museum in London, where he made significant contributions to its collections of historic microscopes.

One of his key achievements was his work on cataloging and documenting historical microscopes, which helped preserve the legacy of this important scientific tool. His deep knowledge and passion for the subject were shared with a wider audience through his extensive writing. Bracegirdle was also a popular lecturer, and his engaging teaching style left a lasting impact on students and colleagues alike.

Brian Bracegirdle authored numerous books on microscopy and related topics, many of which became essential reading for historians and scientists. His publications include

A History of Microtechnique* (1978)
Microscopes: A Short History* (1978)
Beads of Glass: Leeuwenhoek and the Early Microscope (1983)
Microscopical Mounts and Mounters* (1995),
The Quekett Microscopical Club 1865–2015* (2016),

and several volumes in the *An Atlas of Microscopy* series. These works have cemented his legacy as an authority in the history of scientific instruments. His contributions remain vital to our understanding of the development of microscopy and its role in advancing scientific knowledge.