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An unusual Napier compass

The Napier compass is a particularly compact form of multifunctional drawing instrument that became popular during the second half of the nineteenth century. It is commonly said to have been invented in 1848 by David Napier (1790–1869) the celebrated naval engineer, but as with many origin stories there is a distinct lack of hard evidence. The design itself consists of a turnabout compass folding legs, the steel lower portions of which slot neatly into the hollow shanks of the upper limbs. Due to their relatively late emergence and delicate construction, most Napier compasses were made of German silver rather than brass.

A puzzling little example of the type recently came into my possession. It is slightly smaller than the average (two and a half inches when closed) and housed in a leather slip case with nickel-plated brass ball clasp closure, rather than the usual clamshell case. I assumed the case had come from something else (lipstick, nail clippers, or similar) although it is a perfect fit and has clearly held the compass for many years as evidenced by the wear to the leather.

Stanley aluminium Napier compass details

However, the real oddity is the compass itself. I had purchased it for a very small sum on ebay assuming it was just another unsigned Napier compass, hopefully in reasonable condition. On removing it from the case, what immediately struck me was its weight – it feels as light as a feather – and the unusual whiteness of the metal, clearly aluminium. Inscribed on the side of one leg are the initials “.C.W.H.” and on the other “STANLEY, LONDON.”

In contrast to the white metal, the washers of the sector joint are pitch black. Under magnification they appear to be made of vulcanite or similar, rather than the usual steel plates, presumably to prevent excessive wear of the relatively soft aluminium. The only steel parts of the compass are the pivots and the lower legs with their rotating points.

Stanley aluminium Napier compass open

I was aware that Stanley had filed a patent in 1861 for the “Application of aluminium to the manufacture of mathematical instruments” (No. 3092), but had never come across any actual examples. Indeed, just seven years later Stanley had the following to say about aluminium in the third edition of his Mathematical Drawing Instruments:

“Attempts have been made to introduce aluminium and its alloy, aluminium-bronze, into the manufacture of drawing-instruments – it must be admitted, with little success. Aluminium would undoubtedly in some respects be very excellent, especially for its non-corrosive quality and extreme lightness; but it requires some genius to discover the method of soldering it to steel, to render it at all adapted to drawing instruments.”

Of course, the joints of a folding compass are pivots and would not require soldering, so it is possible that Stanley continued to use aluminium for these, where the weight advantage would also be most appreciated. On the other hand, the 1908 Stanley catalogue offers Napier compasses in electrum and silver only. I hope at some point to check the earlier editions of Stanley’s catalogue and book for any mention of the aluminium Napier. In the meantime, I’d be interested to discover if any other pocket compasses originally came with this kind of case, or if it was simply a convenient way to protect the compass when carried in the pocket.

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