Allan Mills

An Alkalophilic Red Halophilic Bacterium with a Low Magnesium Requirement from a Kenyan Soda Lake

Summary: A Halobacterium species isolated from solar evaporation ponds and sodium sesquicarbonate deposits at Lake Magadi, Kenya, differs from known species of Halobacterium in its GC content, in being obligately alkalophilic with a pH optimum between 9.0 and 10.0, and in having a Mg2+ requirement of between 0.1 and 2.0 mm for optimum growth.

An Alkalophilic Species of Ectothiorhodospira from a Kenyan Soda Lake

Summary: An Ectothiorhodospira sp. was isolated from an alkaline mud sample from Lake Hannington, Kenya. It closely resembled Ectothiorhodospira shaposhnikovii in its ultrastructure, GC content, photosynthetic pigments, flagella position and mode of sulphur deposition, but differed in exhibiting more extreme alkalophily, the pH optimum being 9·0 to 9·5, and in being obligately phototrophic.

The coefficient of friction, particularly of ice

The static and dynamic coefficients of friction are defined, and values from 0.3 to 0.6 are quoted for common materials. These drop to about 0.15 when oil is added as a lubricant. Water ice at temperatures not far below 0 °C is remarkable for low coefficients of around 0.05 for static friction and 0.04–0.02 for dynamic friction, but these figures increase as the temperature diminishes. Reasons for the slipperiness of ice are summarized, but they are still not entirely clear. One hypothesis suggests that it is related to the transient formation of a lubricating film of liquid water produced by frictional heating. If this is the case, some composition melting a little above ambient temperatures might provide a skating rink that did not require expensive refrigeration. Various compositions have been tested, but an entirely satisfactory material has yet to be found.

The mercury clock of the Libros del Saber

Summary The Libros del Saber de Astronomia is a compilation of various Arabic astronomical works translated into Castilian in the second half of the thirteenth century, under the direction of King Alfonso X of Spain. A section describing a mercury clock has been suggested to be of particular significance in view of the likely invention of the mechanical clock around this period, so a new translation into modern technical English has been prepared. The clock is shown to consist essentially of an annulus of mercury-filled chambers separated by narrow partitions, each partition being perforated by a very small hole. This annulus is attached concentrically to a pulley wheel around which a cord is wrapped, and a fixed weight hung upon the cord. The torque raises the mercury on the opposite side, but as the resulting hydrostatic head then causes it to percolate through the holes connecting the chambers the wheel slowly rotates to maintain its equilibrium. The weight therefore gradually descends in a controlled ...

An inexpensive digital infrared camera

Details are given for the conversion of an inexpensive webcam to a camera specifically sensitive to the near infrared (700?1000?nm). Some experiments and practical applications are suggested and illustrated.

The ball-bearing electric motor

A working model of the ball-bearing electric motor which may be constructed from readily available materials is described. Schematic circuit of a suitable AC/DC power supply which can be used for the motor is shown.

Early voltaic batteries: An evaluation in modern units and application to the work of Davy and Faraday

Classic voltaic batteries of the silver/zinc and copper/zinc types are the ancestors of todays primary cells, and facilitated the development of many aspects of electrical technology. Nevertheless, they appear never to have been studied and evaluated in a quantitative manner, with results recorded in terms of volts, amps, ohms, and watts. Research of this nature is reported here, and has been conducted for the most part with copper/zinc cells. Log–log graphs of voltage versus load and current, and power versus load, are presented for many electrolyte systems. It has been shown that, although the textbook electrolyte of dilute sulphuric acid does work, it is an order of magnitude inferior to a solution containing some additional nitric acid. The latter diminishes the current‐limiting phenomenon of polarization, and was in fact used by Davy, Faraday, and other early investigators. A quantitative consideration of Nicholson and Carlisles discovery of the electrolysis of water with a silver/zinc voltaic pile is followed by examination of the electrolysis of pure water, trough batteries, and Davys isolation of potassium and sodium. Every battery gives maximum power when its resistance is adjusted (by appropriate series/parallel connections) to match the resistance of the load: the maximum output of the ‘Great Battery’ of the Royal Institution is assessed at no more than 3 kW. The paper concludes with a note on the recognized hazard of long‐term exposure to mercury vapour (produced by amalgamation of zinc electrodes in batteries) and its possible relevance to the health of Michael Faraday.

Who invented the O-ring?

Abstract As a commercial product the O-ring is ideal: simple, effective, and easily mass-produced; yet hard to make oneself on a one-off basis. With so many millions in past and present use the inventor of the O-ring deserves to be both rich and famous, but in fact the origin of the device is far from clear.

Altitude sundials for seasonal and equal hours

Summary Altitude sundials do not require knowledge of the N-S direction to quantify time in terms of either seasonal or equal hours. Methods for determining the corresponding dial patterns are reviewed, and accurately computed data for a latitude of 51°N presented as horizontal, vertical, rectangular, and pillar dials on both timekeeping systems.

The hydraulic ram (or impulse) pump

The hydraulic impulse pump utilizes a fraction of the momentum of a flowing stream to lift a small portion of that water to a higher level. There it may be accumulated in an elevated cistern to provide sufficient water for several families, for the pump works 24 h a day with no additional source of energy. The operation of the pump is described, along with a working demonstration model constructed from plastic waste pipe and fittings.