Question: How did scientists measure sea levels prior to instrumental measurements?
About the article "Climate change", section "Sea level change".

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Global sea level change for much of the last century has generally been estimated using tide gauge measurements collated over long periods of time to give a long-term average.
More recently, altimeter measurements — in combination with accurately determined satellite orbits — have provided an improved measurement of global sea level change.
To measure sea levels prior to instrumental measurements, scientists have dated coral reefs that grow near the surface of the ocean, coastal sediments, marine terraces, ooids in limestones, and nearshore archaeological remains.
The predominant dating methods used are uranium series and radiocarbon, with cosmogenic radionuclides being sometimes used to date terraces that have experienced relative sea level fall.
In the early Pliocene, global temperatures were 1–2˚C warmer than the present temperature, yet sea level was 15–25 meters higher than today.
Satisfaction of the conditions of conjoint measurement means that measurements of the levels of "A" and "X" can be expressed as either ratios between magnitudes or ratios between magnitude differences.
It is most commonly interpreted as the latter, given that most behavioural scientists consider that their tests and surveys "measure" attributes on so-called "interval scales" .
That is, they believe tests do not identify absolute zero levels of psychological attributes.
Formally, if "P", "A" and "X" form an "additive conjoint structure", then there exist functions from "A" and "X" into the real numbers such that for "a" and "b" in "A" and "x" and "y" in "X":formula_15.
If formula_16 and formula_17 are two other real valued functions satisfying the above expression, there exist formula_18 and formula_19 real valued constants satisfying:formula_20 and formula_21.
That is, formula_22 and formula_23 are measurements of "A" and "X" unique up to affine transformation (i.e.
each is an interval scale in Stevens’ (1946) parlance).
The mathematical proof of this result is given in .
This means that the levels of "A" and "X" are magnitude differences measured relative to some kind of unit difference.
Each level of "P" is a difference between the levels of "A" and "X".
However, it is not clear from the literature as to how a unit could be defined within an additive conjoint context.
proposed a scaling method for conjoint structures but he also did not discuss the unit.
The theory of conjoint measurement, however, is not restricted to the quantification of differences.
If each level of "P" is a product of a level of "A" and a level of "X", then "P" is another different quantity whose measurement is expressed as a magnitude of "A" per unit magnitude of "X".
For example, "A" consists of masses and "X" consists of volumes, then "P" consists of densities measured as mass per unit of volume.
In such cases, it would appear that one level of "A" and one level of "X" must be identified as a tentative unit prior to the application of conjoint measurement.
If each level of "P" is the sum of a level of "A" and a level of "X", then "P" is the same quantity as "A" and"X".
For example, "A" and "X" are lengths so hence must be "P".
All three must therefore be expressed in the same unit.
In such cases, it would appear that a level of either "A" or "X" must be tentatively identified as the unit.
Hence it would seem that application of conjoint measurement requires some prior descriptive theory of the relevant natural system. 
Langley invented the bolometer, an instrument for measuring infrared radiation.
The bolometer has enabled scientists to detect a change of temperature of less than 1/100,000 of a degree Celsius.
It laid the foundation for the measurements of the amount of solar energy on the Earth.
His 1881 paper, The Bolometer and Radiant Energy, became a scientific classic.
He made one of the first attempts to measure the surface temperature of the Moon, and his measurement of interference of the infrared radiation by carbon dioxide in Earth's atmosphere was used by Svante Arrhenius in 1896 to make the first calculation of how climate would change from a future doubling of carbon dioxide levels. 
Jason-1 is a satellite oceanography mission to monitor global ocean circulation, study the ties between the ocean and the atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño and ocean eddies.
It is the successor to the TOPEX/Poseidon mission, which measured ocean surface topography from 1992 through 2005.
Like its predecessor, Jason-1 is a joint project between the NASA (United States) and CNES (France) space agencies.
Jason-1's successor, the Ocean Surface Topography Mission on the Jason-2 satellite, was launched in June 2008.
These satellites provide a unique global view of the oceans that is impossible to acquire using traditional ship-based sampling.
Jason-1 was built by Thales Alenia Space using a Proteus platform, under a contract from CNES, as well as the main Jason-1 instrument, the Poseidon-2 altimeter (successor to the Poseidon altimeter on-board TOPEX/Poseidon)Jason-1 was designed to measure climate change through very precise millimeter-per-year measurements of global sea level changes.
As did TOPEX/Poseidon, Jason-1 uses an altimeter to measure the hills and valleys of the ocean's surface.
These measurements of sea surface topography allow scientists to calculate the speed and direction of ocean currents and monitor global ocean circulation.
The global ocean is Earth's primary storehouse of solar energy.
Jason-1's measurements of sea surface height reveal where this heat is stored, how it moves around Earth by ocean currents, and how these processes affect weather and climate.
Jason-1 was launched on December 7, 2001 from California's Vandenberg Air Force Base aboard a Delta II rocket.
During the first months Jason-1 shared an almost identical orbit to TOPEX/Poseidon, which allowed for cross calibration.
At the end of this period, the older satellite was moved to a new orbit midway between each Jason ground track.
Jason has a repeat cycle of 10 days.
Orbit maneuvers in 2009 put the Jason-1 satellite on the opposite side of Earth from the Jason-2 satellite, which is operated by the U.S. and French weather agencies.
Jason-1 now flies over the same region of the ocean that Jason-2 flew over five days earlier.
Its ground tracks fall mid-way between those of Jason-2, which are about apart at the equator.
This interleaved tandem mission provides twice the number of measurements of the ocean's surface, bringing smaller features such as ocean eddies into view.
The tandem mission also helps pave the way for a future ocean altimeter mission that would collect much more detailed data with its single instrument than the two Jason satellites now do together.
The program is named after the Greek mythological hero Jason. 
There are many types of penetrometer designed to be used on soil.
They are usually round or cone shaped.
The penetrometer is dropped on the test subject or pressed against it and the depth of the resulting hole is measured.
The measurements find whether the soil is strong enough to build a road on.
Scientists also use a penetrometer to measure how much moisture is in soil.
Penetrometers are used on space probes such as the Cassini–Huygens probe, to measure the amount of moisture in soil on other planets.
Penetrometers are furthermore used in glaciology to measure the strength and nature of materials underlying a glacier at its bed.
A penetrometer is also used in longer professional cricket matches, to measure how the pitch is holding up over the course of a multi-day match.