Artuur.—On Skew Arches. 265 
ArT. XXIIL—On Skew Arches. By W. Artuor, C.E. 
Plate. 
[Read before the Otago Institute, 3rd October, 1876.) 
Ix introducing to your notice such a dry subject as that of this paper, my 
excuse must be, that in these days of great public works in the colony, its 
consideration níay prove useful, more particularly as the best authorities, 
such as ** Buck, on Oblique Bridges,” cannot be got at all here ; and another 
thing is that, being confessedly a difficult subject, it may be found all the 
more deserving of some attention, at any rate from engineers. But before 
describing particularly the details of the design of a skew arch, it may not 
be altogether uninteresting to look for a little at what is known of arches in 
general, built during past ages of the world, and also at the position of 
bridges in Otago at the present day. 
History of Arches. 
Arches of masonry—that is, ordinary arches—are of very ancient origin. 
The earliest known remains are to be found in the ruins of Nineveh ; they 
occur next among the oldest buildings of ancient Egypt. The caves of 
Adjunta and Ellora in British India reveal to this day circular and pointed 
arches in their subterranean temples, shewing the skill and handicraft of a 
race of men who lived probably three thousand years ago. Dr. Robinson, 
the American traveller, discovered at Jerusalem, part of a very old arch, 
which appears to have connected Soloman's Temple with a portion of the 
city, from which it was separated by a small valley or gorge. He found 
only a few stones still in position at the springing of the arch next the 
temple, or what is now the mosque, but these were of very great dimensions. 
From measurements made across the valley, the span of this arch was found 
to be about 350 feet. I have calculated the weight of one of these arch 
stones from such dimensions as are given, assuming the material to be lime- 
stone, and it turns out to be twenty tons! The Romans next appear to 
have availed themselves of the principle of the arch, as may be seen in their 
domes, bridges, vaults, and sewers. And lastly, in the explorations which 
were made forty years ago in Mexico, together with pyramids and ancient 
cities, several specimens of arches also came to light, which are believed to 
be at least two thousand years old. It thus appears that the principle of 
the arch was known and appreciated from the earliest ages. In modern 
times the construction of arches has received greater attention, but we have 
no knowledge of the existence in ancient or modern times of a skew arch, 
until 1530, when one was built in Italy. In our own country, no attempt 
was made to erect such a structure, until the introduction of railways com- 
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