South Thames Discussion Group
Saturday 4th March 2017
This was the 28th meeting of the Group, and the second to be held at the Trinity Centre in Wallington in south-west London and organised by Albert Greenfield. The meeting started with coffee, tea and biscuits followed by three entertaining talks before lunch. The talks were recorded and will be available in the Members’ area of the website.
Phil Greaves spoke on “Whisky and Waterfleas”, telling us of his love for the scenery in Scotland and his fascination with Cladocera, some of which eat algae and others of which are predatory. The most recent key to British species is by two Quekett members, D. J. Scourfield and J. P. Harding, (FBA Scientific Publication No. 5) and is becoming dated, but there is a more modern key to the Cladocera of France. Phil travels with a folding boat on top of his Land Rover so that he can sample waterfleas away from the shore and in deep water; he can sample down to 60 feet below the surface. Phil explained his methods for collecting, labelling and storing Cladocera. Phil sends his records to the Biological Records Centre, and has found 2 species new to Scotland and extended the known distribution of others. The Cladocera Interest Group encourages identification and study of water fleas.
Phil Greaves lecturing
After Phil had answered questions from the audience, Club President Carel Sartory surprised him by announcing that he had been elected an Honorary Member of the Club and presenting him with a certificate.
Carel Sartory presenting Phil Greaves with Certificate of Honorary Membership
Brian Davidson spoke on Powell & Lealand’s No. 1 stand, a large and versatile brass microscope from the Victorian era, starting with some illustrations of the Great Exhibition of the Works of Industry of All Nations in Hyde Park in 1851, a celebration of industrial technology and design. Brian explained the various versions of Powell & Lealand’s stand from the early 1860s to around 1914 and how it was both criticised and copied by other manufacturers. The company never had more than 5 employees and so their microscopes were not made in large quantities; probably not more than 600 No. 1 stands were made and there was a 12-month waiting list. Sadly, many of them have been broken up to remove a graduated scale that was made of platinum instead of brass to avoid corrosion.
Brian Davidson lecturing
Carel Sartory told us about all sorts of items that are not designed for use by microscopists but that can be very useful, including corned-beef tins (diatom scrapers), plastic bottles (underwater traps), coffee filters, cocktail sticks, icing bags, wok skimmers and strainers, lidocaine throat spray (anaesthetic for pond life), table tennis balls and translucent kitchen bowls (diffusers), and credit cards and cheese slicers (scraping diatoms from mud surface).
Carel also told us about microscopical specimens from unusual sources, including scales from fresh fish, brushings from oyster shells (good source of diatoms) and paracetamol tablets (crystallise on slides).
Carel Sartory lecturing
After the lectures, we all sat down for lunch, shepherds pie with broccoli and carrots, followed by apple pie with custard.
Ruth Humphreys, Jacky McPherson, Paul Smith and Carel Sartory at lunch
After lunch, several members set up their exhibits.
Carel Sartory showed several of the items mentioned in his talk, including a gherkin lifter, a cheese slicer, a disposable icing bag, a tiny soy-sauce bottle, a tray for expensive chocolates, a stack of plastic containers, coin capsules, a large syringe, and of course illuminators made from strips of LEDs
Carel Sartory’s exhibit
One of Carel’s LED illuminators was connected to a power supply to show how effective this type of side light can be.
Sand illuminated by LED strip
Brian Davidson showed his Powell & Lealand No. 1 stand and a box full of accessories, including objectives from 4″ to 1/16″, eyepieces, prisms, reflectors and tweezers. The Lieberkühn reflectors even had screw-on caps to protect the reflective surface. The stand is very heavy, with a substantial cast base so that it remains stable even when tilted.
Powell & Lealand No. 1 stand and accessories
Nigel Williams brought a sample of pond water with live rotifers for us to examine under his Wild M20 microscope.
Winifred Greenfield and Nigel Williams
Nigel also showed a photograph of a Valentine diatom arrangement by Klaus Kemp.
Valentines diatom arrangement by Klaus Kemp
Joan Bingley brought two specimens of petrified wood that she had found in a spoil heap in Patagonia (once part of the ancient supercontinent Gondwana) for us to examine under her stereomicroscope. The growth rings and cell walls that have been substituted by rock could be seen. The specimens showed signs of having been worked to produce sharp edges.
Phil Greaves used his Wild M11 microscope to show a live specimen of Daphnia obtusa Kurz under darkground illumination; we could easily see eggs, and the heart beating.
Phil Greaves’ exhibit on Cladocera
The specimen was confined under a coverslip that was raised slightly from the slide.
Daphnia obtusa under the microscope
James Rider brought a Swift FM-31 portable microscope to which he had added a patch stop for dark-ground illumination. To demonstrate how well it worked, James used a circular diatom arrangement on a slide sold by W. Watson & Sons.
Swift FM-31 portable microscope
James attached his stops to 20 mm coverslips that fit nicely on top of the 20 mm light source. He had experimented with several different sizes punched from 250 gsm black card, and was surprised that best results were with an 18 mm stop, only slightly smaller than the light source.
James also brought an old (c. 1929) Beck stereomicroscope called the Biomax Magnifier that was supplied with high and low power eyepieces and a pair of objectives that can be inverted to change the magnification.
Beck Biomax Magnifier
James brought 2 dry mounts of insects that he had made at Belstead House in 2003 under the supervision of Ernie Ives, with 2 small LED torches (supported on a mobile telephone holder) to illuminate them under the stereomicroscope.
Dry mount of entire ground beetle (Pterostichus melanarius (Illiger))
Jacky McPherson brought a photograph of E. D. Evens potholing, a binder full of information that she had collected about him, and some Postal Microscopical Society notebooks with hand-written entries by him. Jacky has recently learned that there are another 90 PMS notebooks with entries by E. D. Evens.
Deborah Bishop, Winifred Greenfield and Jacky McPherson (right)
PMS notebooks with entries by E. D. Evens
Joan Bingley brought the Quekett shop-in-a-box, an assortment of items that are normally only available by post. Ray and Cherry Trapmore can’t get to most microscope meetings so this gives visitors the opportunity examine items and to avoid postage charges.
Alan Wood brought his Olympus CH-2 microscope with a brightfield/darkfield vertical illuminator, used in darkfield mode with biological specimens including feathers, lichen, butterfly wings and crocus stamens. The illuminator pipes light down a cylinder surrounding the special Neo objectives to give reflected darkfield illumination. Through the microscope, the depth of field is extremely shallow (around 0.05 mm for the 5× objective), but Alan also showed colour photographs of the same specimens with good depth of field produced by stacking series of images with Zerene Stacker.
Alan Wood’s exhibit
Lichen-encrusted twig under the microscope
Stacked image of yellow lichen (Neo 5× objective, FK 2.5× photo eyepiece, stack of 44 images, 1.75 mm depth of field)
After we had all had the opportunity to examine and discuss the exhibits, Carel Sartory thanked Albert Greenfield for organising another successful meeting, and we enjoyed another round of tea, coffee and biscuits before departing.
Report and photographs by Alan Wood