| Date | 1880 |
| Author | Anon. |
| Contribution | Oil-immersion objectives took over from water-immersion objectives for the most demanding microscopical work. |
| Reference | Bradbury |
| Notes | Lenses with numerical aperture of 1.3 or more were being produced not only by Zeiss (under Abbe's direction) but also by such expert manufacturers as Tolles, and Powell and Lealand. |
| Category | Microscopy |
| Pathogen Class | General |
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