The wheel aperture is not that common on Grubb lenses. We have examples of lenses where Howard added a diaphragm such as my aluminium lens No 5350, the highest number on a Grubb lens found to date, and No 4009 which is definitely an 'updated' lens with a number that would date as coming from as far back as the 1870s. The latter was found in the collection of the Photographic Society of Ireland, of which Howard was President in 1888 and 1889.Originally Posted by pgk
What is most pleasing about Grubb No 5281 is that it is in the home where Charles Parsons grew up. The contribution of Charles to the optical industry is not recognised very much, probably because of his great achievements in other areas. The following is a good summary by R H Parsons, published by The British Council, of what he achieved in the field of optics. His involvement with the Ross company and in the field of optical glass are noteworthy.
PARSONS' OPTICAL WORK
The interest that Parsons took in matters connected with optics was no doubt largely hereditary, his father, Lord Rosse, having been a well known astronomer and famous as the constructor of the great 6-foot reflecting telescope at his country seat at Birr, in Ireland. An early outcome of this interest was the development of parabolic and parabolic-elliptic reflectors for searchlights, by which Parsons contributed so greatly to military and naval defence. He built up what became probably the most important business in the world devoted to the manufacture of such reflectors, but it was not until after the first great war that he turned his attention to optical work generally.
His first step was to acquire in 1921 a controlling interest in the firm of Ross, Ltd., of Clapham, London, well known as makers of binoculars and other small optical apparatus of the highest class. Here he introduced various improvements in the methods of glass grinding, but soon turned his mind to the much larger question of the manufacture of optical glass itself. Prior to 1914 an important part of the optical glass used in this country had been imported from the Continent. When this source of supply was no longer available, due to the outbreak of war, the position became serious because, quite apart from the ordinary requirements of industry, the efficiency of the fighting services could not be maintained without adequate supplies of the special kinds of glass needed for rangefinders, periscopes, field-glasses and other optical instruments necessary to war. The Government therefore took action which resulted in the establishment of an optical glass factory near Derby, and so ensured an adequate provision for the Services. More than this was indeed accomplished, for it was demonstrated that British experts could manufacture optical glass which was superior in many respects to the over-praised products of the German factories.
With the great reduction in the demand for optical glass that was brought about by the termination of the war, the Derby factory fell upon evil days, and in spite of the warning that had been received as to the danger of depending upon foreign countries for an essential war requirement, it appeared probable that the works would have to be closed. At this juncture Parsons appeared upon the scene, and inspired far more by public-spirited motives and by scientific interest than by any idea of making money, he purchased the entire factory in 192I. Under the name of the Parsons Optical Glass Company, the undertaking acquired a new lease of life, thanks to his energetic direction. The making of optical glass had always been very much of a secret process, understood by few and conducted along more or less traditional lines. Such conditions inevitably lead to a stagnation of practice, and to the conservation of somewhat primitive methods of manufacture. Parsons was not bound by the precedents of the industry, and he at once applied his wonderful mechanical and scientific knowledge to the improvement of the processes employed. He devised better ways of melting the glass and of stirring it in when molten, while he also introduced the practice of running the melted glass directly into a mould for immediate transference to the annealing furnace. By these and other improvements he was able to make exceptionally good discs of optical glass of any size required and possessing such special properties as might be demanded, Under his management the works produced about one hundred different kinds of glass for optical purposes, each best suited for some particular duty.
Parsons certainly did a great deal to establish the excellent reputation that English optical glass now enjoys all over the world, but according to his friend and colleague, Dr Gerald Stoney, F.R.S., he spent a fortune in the task, for his enterprise is said to have cost him something like £60,000. After his death the factory was acquired by the old-established firm of Chance Brothers of Birmingham, whose name is well known in connection with optical glass manufacture.
His success in producing large discs of optical glass for the objectives of astronomical telescopes led Parsons to take an increasing interest in the' telescopes themselves, the construction of which appealed both to his scientific and mechanical instincts. He had, from his childhood, been well acquainted with the Grubb family of DubIin, who had built notable astronomical instruments, and he had made glass for the lenses of some of their telescopes. During the first world war, Sir Howard Grubb and Sons, Ltd., transferred their optical works to England, establishing a factory at St Albans in Hertfordshire, but after the war their business went into liquidation and there was a likelihood of the works being closed altogether. Parsons determined to save the old-established undertaking, and in 1925 he purchased the assets of the firm and continued its activities under the name of Sir Howard Grubb, Parsons and Co. He built new works for it at Walkergate, adjacent to his turbine works at Heaton, and under his direction it started afresh upon a prosperous career. Many notable instruments have been constructed at Walk erg ate, including a 36-inch reflecting telescope for Greenwich Observatory and two 74-inch reflectors, one for the Dunlap Observatory of the University of Toronto and the other for the Radcliffe Observatory at Pretoria. These latter instruments are the largest in the British Empire.
William
Reply With Quote
Bookmarks