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Charles Piazzi Smyth
Photography, Magnesium, and the Pyramid
1865, 22 September
The Mechanics' Magazine, September 22, 1865, p. 179
Photography, Magnesium, and the Pyramid.
Mb. W. White exhibited photographs of the interior of the Great Pyramid, taken with magnesium light, by Professor Piazzi Smyth. Mr. White observed that one of the first persons to suggest the above undertaking was though Scottish Astronomer Royal. Probably all have heard something of though interesting controversy connected with the granite coffer the sanctieii sanctorum of the Great Pyramid. It was Professor Piazzi Smyth's great object to bring this mysterious coffer to light, and to dissipate for ever all uncertainty about it. This, with the aid of magnesium, he has accomplished. We shall shortly have a volume from his pen descriptive of his researches and conclusions, and illustrated with photographs. Meanwhile he has most kindly allowed copies of his photographs to be exhibited to the Association, and has favoured me with a few notes concerning them which I shall now read. 1st. The interior of the Great Pyramid did not prove a good space for developing the excellences of the magnesium light. The ventilating passages opened by Colonel Howard Tyse in 1837 have been completely stopped up with stones and sand by the Arabs. Hence the air in the interior of the Pyramid has no visible means of being changed or purified, and as the said interior is visited every day through six months in the year by numerous parties of visitors bearing candles, the oxygen is so deficient, and the carbonic acid so abundant, that my surprise is that the magnesium burnt at all. It did burn, but in a languid sort of way, and the smoke it threw off remained suspended in the motionless air for twenty hours or more, so that only one picture could be taken in twenty-four hours. If a second was attempted, the illuminated smoky air intervening between [the camera and the object desired to be pictured, was the only result on the photographic plate. 2nd. My object was not pictorial or artistic photography (of which I have therefore nothing to show), but the application of photography to certain disputed and special parts of the interior of the Pyramid for the sake of scientific examination and measurement; and these objects were obtained, notwithstanding all the drawbacks of the place, which really seemed combined to frustrate the merit of the light. 3rd. One example of success is presented in the granite coffer in the King's Chamber of the Great Pyramid. According to the theory of the late Mr. Taylor, that coffer was a primeval measure of capacity, from whence is derived the hereditary Anglo-Saxon wheat-measure called the quarter, of which coffer it is the fourth part. Whilst, however, we know by Act of Parliament how many cubic inches are contained in four quarters English, there has been much doubt ns to the cubical contents of the granite chest of the Pyramid. The measures of the French Academy in 1799 made it nearly 6,300 cubic inches greater than several English travellers had declared it to be, though they again by no means agreed with each other in subsidiary details. Now, however, by means of the magnesium light, we have a series of photographs of this coffer, with a system of measuring rods fastened about it, showing the size inside and the size outside; and finally, the cubical contents being summed up, prove that the remarkable granite vessel is a measure of capacity equal with almost mathematical accuracy to three quarters English.
Considerable discussion was evoked by the above paper, and Mr. White, in answer to inquiries, observed that castings could now be made of magnesium, although only a short time ago it had been prophesied that they could not accomplish that object, as it would so soon take fire. Magnesium could not be soldered. A good deal had been done towards cheapening the metal, and if supplied in large quantities now it could be had at a great reduction in price. No general application had as yet taken place with magnesium for illuminating purposes. Mr. Mather was the first person who had converted magnesium into wire. Mr. White bad been informed that a photographer in Rome had received a commission to photograph the interior of the catacombs.