Early Aluminum surveying instruments are a very cool collectible, and have an interesting history. Here's what you need to know:

The metal alumina was first discovered around 1825. Producing aluminum was a very complex process, however, so only very small quantities were produced, which made aluminum very expensive.

A new process of producing Aluminum was invented in 1856, which allowed for a significant increase in production. This of course dropped the price of aluminum somewhat as well. The increase in production and decrease in prices motivated many to consider the commercial applications of Aluminum.

One of the primary benefits of aluminum is that it weights significantly less than other metals. Given the weight of surveying instruments in the second half of the 19th century, it isn't surprising that many thought of making instruments out of aluminum rather than brass. The weight savings could be up to 75%. That's like trading in a 12lb laptop for a 3lb laptop. That's a No-Brainer for people who live on the road.

Gurley made the first Aluminum surveying instrument in America in 1876. It was more of a proof of concept instrument than anything else. Aluminum was still a very expensive metal, and there wasn't much of it around. Plus, some were starting to have concerns about how Aluminum would interact with other metals (Aluminum expands at different rates than say brass does). And since Aluminum was a very soft metal, other worried about whether aluminum could hold up to the rigors of surveying. Others also worried about whether Aluminum would attract the needle, or how stable the light instruments would be on windy days.

Very few surveying instruments were made out of aluminum until the late 1880s, largely because of price. In 1886 two researchers independently created the same manufacturing process that allowed for a very large increase in production, along with a significant decrease in price. Making surveying instruments out of Aluminum became a commercially viable opportunity.

A good number of instruments makers experimented with making instruments out of Aluminum. Given the softness of aluminum, these makers used an Alloy, made up largely of Aluminum plus a smaller amount of another metal, like copper. Adding a bit of copper made the Aluminum harder and more rigid. Too much copper made the Aluminum very brittle.

In the late 1880s and early 1890s, two camps formed regarding the wisdom of making surveying instruments out of Aluminum. On the one hand, the major makers (Gurley, Buff & Berger, K&E and Young & Sons) advised against making major instruments out of Aluminum. Buff & Berger was in fact adamantly opposed, as they published in their 1889 Catalogue - Buff & Berger 1889 Bashing Aluminum. Definitely worth a read as this will explain the major pitfalls of making instruments out of Aluminum. You also had some surveyors who used aluminum instruments state their disapproval in print. Here is a nice 1892 blurb by Bennett Brough, who authored an 1891 textbook on mine surveying - Brough 1892 Aluminum Wear Problems. It's worth noting, however, that even some of the makers who advised against making aluminum instruments would make an aluminum instrument if requested by a customer - See Gurley 1895 Manual.

On the other hand, a number of smaller instruments makers (primarily Lietz and Queen) jumped on the Aluminum instrument bandwagon. These makers saw the upside of selling full-sized surveying instruments that weighed half as much or less than their brass equivalents. They recognized however that Aluminum should not be used for certain bearing parts - that many transit parts still needed to be made out of brass to maintain precision. Lietz in particular was very pro-Aluminum, and published testimonials from surveyors who used Lietz Aluminum Instruments - Lietz 1897 Testimonials.

Note - A customer typically paid about a 15% premium to have an instrument made out of Aluminum compared to Brass. 1893 Lietz 15% Extra. Sala 1896 15% price increase up to 50% weight savings.

The 1893 World's Fair in Chicago brought many instruments makers together to exhibit their wares. An article discussing the exhibits by Engineering News focuses on each maker's viewpoint on Aluminum - definitely worth a read. 1893 Worlds Fair Chicago - Makers State Viewpoint.

It appears that only a limited number of Aluminum surveying instruments were produced between Gurley's 1876 aluminum transit and 1900 or so. Gurley for example said that they only made a handful of special order Aluminum Solar Compasses. Queen hoped to make a big splash with their Aluminum surveying instrument exhibition at the 1893 World's Fair, but those hopes were dashed. There are only two known Queen Aluminum Transits, and those instruments were made close in time to the World's Fair based on their serial numbers. Young & Sons evidently made some pre-1900 Aluminum instruments, as a few have survived or were otherwise documented (check out this FANTASTIC 1882 Y&S Solar Compass). But for the most part pre-1900 Aluminum surveying instruments are quite scare.

Instruments made out of Aluminum post-1900 appear to more numerous. Lietz, which claimed to have sold over 1000 Aluminum instruments in its 1908 Catalogue, was obviously an enthusiastic supporter of Aluminum, with some reservations. Some other makers, like Young & Sons, also started to incorporate Aluminum non-bearing parts in their instruments.

Notwithstanding the Lietz testimonials, it seems like Aluminum instruments didn't offer a great user experience. For example, the USGLO purchased a good number of Y&S Solar Transits (which featured some Aluminum parts) in 1911 but had various issues with the instruments, including issues with the use of Aluminum. USGLO Chubb Letter re Corrosion. It is also worth noting that some collectors report that the the Aluminum in their Lietz transits has become pretty brittle.

Ultimately, surveying instruments did grow smaller and lighter, but it wasn't the use of Aluminum that made the reductions in size and weight possible. As Buff & Berger indicated in their 1889 Catalogue, improvements in manufacturing techniques would lead to smaller and lighter instruments without sacrificing quality or precision.

While Aluminum surveying instruments didn't pan out as many had hoped, an early Aluminum instrument will make a wonderful addition to any surveying instrument collection. They have a neat look, and a certain "WOW" factor when you pick it up and see how light the instrument is.

BACKGROUND READING:

Bedini 1986 Professional Surveyor Article of Aluminum Surveying Instruments

Rittenhouse Journal - 1987 Kamrass Aluminum Transit Article

WIKIPEDIA - History of Aluminum