Conserving a Colonial Instrument

Colonial instruments specialist and conservator Jeff Lock visited the Historical Society last week to perform treatment on a special piece in our collection.


Our David Rittenhouse surveyor’s level is a telescope with a precision level.  It is an eighteenth-century surveying instrument most likely used in the field by Rittenhouse himself.  A resident of Montgomery County and renowned astronomer, instrument maker, and scientist, David Rittenhouse began making clocks at the age of nineteen.   One of his earliest clocks is in HSMC’s collection (come see it!).  He also made astronomica    l instruments for universities as well as for his own use, like the one in our collection.  In 1769 he was the first person in North America to witness the transit of Venus.  And, with Andrew Ellicott, he finished the survey of the Mason-Dixon Line.

 rittenhouse protrait

The telescope was later used by Alan Corson, county surveyor, in the mid-19th century.  It was his relative, Walter Corson, who donated it to the HSMC in 1900.  Before treatment, the piece had been suffering from a layer of polishing compound residue and a loose gear.  If left in contact with the surface of the piece, the polishing compound residue becomes acidic over time and can actually eat away at the metal.  The loose gear was not only preventing the eyepiece from focusing, but also presented a hazard to the glass lenses.

Copy of Ritt. D. level Loose Gear

Jeff and his associate, Ron Hoppes, came prepared with hand-made screwdrivers, soft brass brushes, and precision measurement instruments.  They carefully removed screws and plates from the tripod base and the telescope, making sure to document the original location of all the pieces.  They then used both nylon and brass brushes with a solution of ethanol and water to gently remove the residue without damaging the existing patina.  The result isn’t shiny, but that’s not what we were looking for!  The piece will now be coated with Renaissance Wax, a petroleum-based conservation wax, which will prevent corrosion in the future.


The experts also extracted the detached gear from inside the telescope and reaffixed the gear to it’s original position.  Now a user can adjust the telescope to focus the eyepiece, as David Rittenhouse intended!  Jeff and Ron completed this treatment in one whirlwind day, and we at HSMC are very grateful for their hard work.

To learn more about Jeff Lock, visit his website at:

And don’t forget to come in to HSMC to see the finished product!



Figure 1, Full telescope: HSMC

Figure 2, Signature: Jeff Lock

Figure 3, David Rittenhouse: HSMC

Figure 4, TPI measurement: HSMC


Treemount Seminary

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The boys in this picture were students at Norristown’s Treemount Seminary, founded in 1844 by Rev. Samuel Aaron, a Baptist minister.  The school was a boarding and day school for boys age 12 to 18.   In 1857, creditors took control of the property (at present day Tremount Avenue and Sandy Street) due to the unpaid debts of the Reverend.  In 1861, John W. Lock leased the property and restarted the school.  This photograph is from that period, perhaps around 1883.  Lock, too, had financial problems and the school closed in 1887.  The school educated about 5000 students in its forty-three year history, including Joseph Fornance II, a US Congressman.  The Treemount Seminary Association was founded by alumni in 1913, and held annual reunions into the 1940’s.

The 1849 curriculum at the school consisted of “Spelling, Reading, Writing, Phonography, English Composition, English Grammar, Elocution, Rhetoric and Logic – in the Latin, Greek, French and German Languages – in Geography, the use of Globes and the rudiments of Drawing – in Arithmetic, Book Keeping and Practical Accountantship – in Algebra and the higher Analysis, and their various applications – in Geometry, Plane, Solid and Analytical and its application to Surveying, Mensuration, Navigation, Engineering and Astronomy – in Natural Philosophy and Chemistry with the aid of good apparatus.”

Tuition was $3.00 per month for day students, and $17.00 per month for boys who boarded at the school.  The school charged an additional $1.50 for each foreign language studied.  Violin and drawing lessons could also be had for an extra fee.


The Historical Society has a collection of the catalogs and circulars from the school, as well as many records of the Treemount Seminary Association including lists of the members and photographs.