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New Leeuwenhoek Microscopes


Figure 5: Microscope from Delft canal. Higher magnifi cation reveals the scratches left by Leeuwenhoek. The lens surface (lower left) had been badly abraded so no magnifi ed image can be created by this microscope. Facets on the central specimen pin show it was cold-forged, whereas replicas are simply turned on a lathe. Note also the neatness of the rivet (upper right), which secures the brass plates together.


Figure 4: SEM macrography of the microscope from the Delft canal. A crew from the British program News At Ten fi lmed studies with the Hitachi S-3400N variable- pressure SEM at the Cavendish Laboratory, Cambridge. We demonstrated that macrographs could reveal fi ne manufacturing details. This example shows the block stage (below), the abraded lens (upper left) and the specimen pin (center) with its positioning knob.


microscope collector, Dr. Tomás Camacho. He sent it to us at Cambridge, England, by secure courier and asked for my opinion. T e microscope seemed to be as authentic as one could judge by appearance ( Figure 3 , #12), though I remained convinced that objective criteria were needed [ 7 ]. T is newly discovered brass microscope from Delſt is very similar to an instrument of undoubted provenance at the Boerhaave Museum (#1), which had been purchased in 1774 at auction from Leeuwenhoek’s possessions and has a documented provenance to the present day. T ough the newly found microscope is not a copy of the original, the screw pitch and dimensions are comparable. T e Boerhaave Museum’s microscope has body plates that are rectangular, whereas the base plates of the newly found microscope have a curved profi le.


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T e Boerhaave Museum has for some years provided replicas of this brass microscope for sale, and thus we have similar instruments—one ancient, one modern—that can be compared. SEM Macrography . As a leading clinical academic, Dr. Camacho shared my preoccupation with criteria of authen- ticity and was eager to encourage further investigations. In the event, his microscope remained with us in Cambridge, England, for fi ve months. A series of macrographs was taken using an Olympus E-500 camera and Zuiko Digital 35 mm macro lens. At the Cavendish Laboratory of Cambridge University, Professor Richard Langford off ered generous access to the SEM suite where Jon Rickard provided much useful advice and access to the Hitachi S-3400N variable-pressure SEM. To invoke macrography, an unusual application for an SEM, an accelerating voltage of 10 kV was used, and the secondary electron image was generated at an initial magnifi cation of 10× or less. T is gave a unique depth of fi eld so that the precise nature of the fabrication methods could be elicited over the entire object. For instance, we can observe the construction of the screw thread and the stage block. We were also able to use energy-dispersive X-ray spectroscopy to determine the elemental components of the brass alloy and the glass from which the lens had been produced.


Correlated microscopy has now allowed us to discern the details of manufacture ( Figure 4 ). We can observe the scratches on the brass surface, the fi nishing of the rivets, and the manufacturing artifacts of the specimen positioning screw and the stage block ( Figures 4 – 6 ). T ese may be unique features of a true Leeuwenhoek microscope and inimitable. Ordinarily, one source of comparison would be the lens, though in this microscope the lens surface has been badly abraded and no longer generates an image.


www.microscopy-today.com • 2015 November


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