The brick-built building housing Twentieth Century Fox stood at 32 Soho Square in the center of London. Their mock-Georgian premises had been completed in 1938, and hundreds of staff worked there, linking to the 8 branch offices spread across Britain. The premises are empty now, and due for development, but they were a center for the British entertainment industry. That same address, 200 years ago, was Robert Brown’s home. He was an astonishingly accomplished microscopist, one of the greatest that science has ever known. Brown is the microscopist who identified the cell nucleus, and from whom Brownian Motion was named. In 1826, 200 years ago, he was researching the structure of the angiosperm ovule. He noted the position and nature of the nucleus and the micropyle (the minuscule aperture through which the pollen tube enters), and he noted that the apex of the ovule is where the future embryo would form … this is all detailed microscopy which anyone today would find difficult and demanding.
In 1976, our country turned 200 years old, The Microscope was in its 39th year of production, and McCrone Research Institute was celebrating its sweet sixteen in Chicago. An annual subscription to the journal cost $30. Here we are fifty years later, and upcoming is the 250th anniversary of the United States, The Microscope turns a respectable 89 years old, McCrone Research Institute is now 66, and by coincidence, a subscription to The Microscope is currently $66. By way of an inflation calculator, the $30 subscription rate in 1976 would be equivalent in purchasing power to $176 today. Do not be too concerned, Microscope Publications are not ready to increase our rates (they are more interested in increasing readership) but we are looking at where the microscope and especially the polarized light microscope stands on the occasion of the Semiquincentennial of 2026, compared to the Bicentennial of 1976.
Thomas Young performed his famous double-slit diffraction experiment in 1801 in which he concluded that light propagated as a wave. The optical diffraction formula credited to Joseph von Fraunhofer for his work with diffraction gratings in 1821 is given by nλ = d sin (θ), where: n is the integer order of the fringe, λ is the wavelength of the light, d is the grating spacing, and θ is the angle of incidence from diffracting grating to the diffraction fringe pattern on a screen. A sieve that has been manufactured to ASTM standards produces a two-dimensional optical diffraction pattern that forms as an interference pattern of diffraction from multiple point sources. The experiment described in this article was performed using four new sieves (200-, 325-, 400-, and 500-mesh) and one clean, used sieve (60-mesh). A 650 nm red laser was used as a source for all 5 sieves. The d-spacing of the various sieves, which is called the "pitch," aperture/hole (opening) plus the wire/bar, was calculated from the optical diffraction equation using the wavelength of the laser light, diffraction pattern measurements, and the distance from the sieve to the wall. For each sieve, the pitch was also estimated from a simple equation involving the mesh value and from estimated ranges (minimum and maximum) of standard values published in ASTM E11-22; Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves.
In the mid-1960s, the Bell System produced a total of five experiment kits, free to any high school teacher or instructor that asked for them. The first three experiments concerned the high technology of the day regarding telecommunications: magnetism, solar energy, crystal growth (transistors), and electronic speech. The fifth experiment simulated the activity of computers of the day. The fourth experiment (Bell System Science Experiment No. 4) taught the students about crystals and light and included the book Experiments with Crystals and Light, a laboratory manual written by Elizabeth Wood, together with minerals, chemicals, and other materials to perform the experiments. Also included was a simple polarized light microscope kit (to build and use) and Wood’s book Crystals and Light: An Introduction to Optical Crystallography to explain the theory behind the observations obtained in the experiments. This paper presents a brief history of the Bell System experiments, describes the contents of the Bell System Science Experiment No. 4, and describes, with images, selected experiments from the laboratory manual.
Separating the particles in a field of view under the microscope into a count of fibers, dander, minerals, tire wear, plant parts, and so on, is of relatively little value if the goal is to assess environmental quality and to suggest ways to improve that quality. Particle assemblages identify sources, the method of generation, and the transport mechanisms that brought those particles to the location in question. With a little training, assemblages can be quickly identified and quantified. This article deals with how assemblages are identified.The human visual system functions at a subconscious level far more efficiently and accurately than conscious processing of the field of view. We use these subconscious functions regularly, at least hundreds or more times a day, though we generally don’t appreciate their analytical value. In Part 1 of this series, we introduced the power of ensemble analysis (see “Particle Source Identification, Part 1: Thinking in Assemblages,” The Microscope, Vol. 72:3, pp. 124–131, 2025; https://doi.org/10.59082/UGIK4736. In this article, Part 2: Assemblages, we introduce "chunk" and "chunking” and how that applies to the analysis of assemblages of particles viewed through the microscope.Recognizing assemblages is an important part of assessing environmental quality. It is also used to determine the origin of honey, characterize paleoenvironments, determine pond water quality, and to identify the source of particles. A number of assemblages are presented here together with how they are identified.
