Riding the wave


For the safety of navigation it is essential to know the position at sea, particularly the longitude . From early historical times til the eighteenth century the method of lunar eclipses was used, as these could be predicted and are observed simultaneously at all points on the Earth when the Moon is above the horizon. However the phenomenon, because of its rarity, was of little use to the crew, also because the determination of contacts was not sufficiently accurate.

Another celestial phenomenon, which allowed to determine the exact time of observation from which to deduce the longitude, was discovered and proposed by Galileo, in 1610, as being superior to the old method of lunar eclipses: it was the observation of the eclipses of Jupiter's satellites, so frequent that it can be observed several times every night.

Still another phenomenon that was proposed by Renaissance astronomers was based on lunar distances. In summary we can say that the Moon moves like the hand of a clock that turns on the "dial" of the sky, so that its position may be indicated at any time by the angle, rapidly changing, that it forms with another star. This angle is the "lunar distance" and, its value, previously calculated for the meridian of reference in the ephemerides, allowed to obtain the time at the meridian of the observer (Capasso 1994).

Already in the fifteenth century ephemerides were compiled by astronomers who observed and studied the motions of the moon to find the laws that made it possible to predict and record, with their coordinates and the subsequent hours of sunshine, the positions of the star on the celestial sphere.

The problem was of great importance to maritime nations, and in the second half of the seventeenth century arose important astronomical observatories, whose aim was the study of the motions of the stars for the determination of longitude: the one in Paris became operational in 1671 and started in 1679 the publication of the Connaissance des temps (later taken by the Bureau des longitudes), that gave the first angular distances of the Moon from the Sun and the major planets; the one in Greenwich , founded in 1675 by Charles II, supported and directed by John Flamsteed , started after a century the publication of the Nautical Almanac, an initiative of the royal astronomer Nevil Maskelyne, and immediately adopted by all maritime nations.

Greenwich Observatory The Greenwich Observatory at the time of its creation, in an etching by Francis Place, kept at the National Maritime Museum

All these methods were still insufficient to solve the fundamental problem, whose solution needed to operate a clock with the time of the meridian of reference indicating exact values by any navigation condition. A timepiece with a perfect regularity, despite the movements of the ship, was required, that, once set at the hour of the meridian, was able to preserve the timing within seconds: a delay of 4 seconds produced an error of 1 minute in longitude.

The first idea to equip vessels with a precision clock dates back to the sixteenth century; it is questionable wether the priority should be attributed to Fernando Columbus, brother of Christopher or to Gemma Frisius (1508-1555), professor at the University of Louvain, of whom was a pupil Mercator . The first one proposed the method in 1524 to the Commission in charge of establishing the line of demarcation between the possessions of the Spanish and the Portuguese, under the Treaty of Tordesillas. Frisius wrote about the benefits of it in De Principi Astronomiae et Cosmographiae (Antwerp 1530), suggesting the use of small mechanical clocks, available at the time.

Willem Barentsz Hut Reconstruction of the hut of Willem Barentsz in "The Threshold of the Unknown Region, London 1876, (Hydrographic Institute of the Navy)

According to tradition, these clocks were first used by the Dutch navigator Willem Barentsz (1550-1597), in his expedition to the polar regions. In the records of the polar expedition by C.R. Markham, an illustration represents the Barentsz hut, as described by Norwegian Captain Elling Carlsen, who found it in 1871, with a clock hanging on the wall, likely a spring clock.

Porcellotti Clock Pendulum clock built by clockmaker E. Porcellotti in the late nineteenth century, according to the indications of Galileo (Florence, Museum of the History of Science )

The first mechanical watches, weight driven, date back to the Middle Ages and were followed by spring clocks, which were developed during the second half of the seventeenth century with the application of the pendulum according to the ideas of Galileo. In 1659 Christian Huyghens (1629-1695) built pendulum clocks suspended to a gimbal, designed to keep them vertical while navigating. The experiments proved unsatisfactory and the project was abandoned.

In 1714, at the initiative of mathematician W. Whiston, in England was formed a Board - the Board of Longitude - which, with the appropriate Longitude Act, raised a prize, with earnings varying from 10,000 to 20,000 pounds depending on the accuracy achieved, for those who could make a marine chronometer able to determine the longitude with an approximation between 1° and 0.5°.

The "challenge" was accepted by John Harrison (1693-1776), a native of Yorkshire, the son of a carpenter, who, lured by the prize, built his first marine chronometer in 1715, consisting mainly of wooden parts.

Harrison's first chronometer The first clock for use on board, by John Harrison in 1735. (Greenwich, National Maritime Museum)

In 1735 he presented the so-called number one, a clock driven not by a massive pendulum, but by two rocker arms connected by wires so that their movements were opposed to each other, counteracting the effects of ship movements. Among other innovations, it had a new type of escapement, two springs, a device that allows its operation even while charging, and a temperature compensating device.

The instrument was tested during a voyage from London to Lisbon on the ship "Centurion", but although the result was positive, the small difference in longitude between the two locations did not permit to certify the performance. So Harrison got only a modest advance on the promised prize , as an encouragement for developing a second model, which also received a second partial prize. It took him more than seventeen years to submit the third watch which, however, like the second one, was only a little smaller than the number one, that weighed about 31 kg.

John Harrison in a painting by King John Harrison in a painting by King at the Science Museum in London (by R.T. Gould, The Marine Chronometer: its History and Development, London 1923, available at the Library of the Hydrographic Institute of the Navy)

It is therefore surprising that his fourth clock, the famous number four, was a nice flat chronometer with a diameter of only 12 cm, not much different from pocket watches used until a few decades ago.

It was tested first, with great success, on the ship Deptford on their way to the West Indies, and a second time on the Tartar, but the prize was not fully paid (and was awarded only in 1773 at the end of his life), as the Board required a review of the mechanism by a group of experts, one of them being the watchmaker Larcum Kendall (1721-1795).

Chronometer number four The number four marine chronometer made by Larcum Kendall in 1769

Kendall in turn made a stopwatch on the model of Harrison's number four, introducing improvements; it was tested in 1772 on the "Resolution" by James Cook , who was enthusiast and used it again in the third voyage. It was also used by J. Vancouver in 1791, during his memorable voyage of circumnavigation in search, along the American coast, of the north-western passage to Northeast.

At the request of the Board, Kendall designed and produced in 1772 and again in 1774, two timepieces, with further modifications to the prototype of Harrison. The Kendall No. 2 had a history of adventure and romance: it was handed over to capt.Phipps for his polar expedition of 1773 and in 1787 was assigned to capt. Bligh.

The timepiece of the Bounty The chronometer of the Bounty: the engraving on the dial says "Larcum Kendall, London (by R.T. Gould, The Marine Chronometer: its History and Development, London 1923)

It was then in the hands of the mutineers of the "Bounty", so it remained at Pitcairn until 1808, when it was purchased by the commander of an american whaling. Stolen to him, years later reappeared in Concepcion in Chile, where it was bought by a Spanish adventurer. At his death in 1840, was eventually sold to a British officer who brought it back to his country: after more than sixty years, the clock was still running, despite its vicissitudes.

As the clocks of Harrison and Kendall were of cumbersome construction and not akin to further improvements, the British government offered a reward to those who could make an improved instrument.

The challenge was taken by Thomas Mudge (1715-1794), another famous clockmaker, who, in 1765, had been a member of the commission to evaluate the timepiece of Harrison. In 1774 he presented his first model, that had a timespan of eight days between charges, and two other models, tested in the eighties, and known as "the Blue" and "the Green", the color of the case. These did not however receive the approval by Maskelyne.

A substantial improvement of those first timers is to be attributed to the french Pierre Le Roy (1717-1785) and to Ferdinand Berthaud (1729-1807), born in the canton of Neuchatel, that after became a major production center in Switzerland.

The first one presented his watch at the Academie des Sciences in 1766 and tested it successfully on the frigate Enjouée in 1768, on a voyage from Le Havre to Newfoundland and back. His major contributions ly in an innovative type of escapement, defined as "à détente", or "on release" and in the compensated rocker arm.

Berthaud moved to Paris in 1745 and in 1762 began to devote himself to watchmaking; he was by far the most prolific author of treatises on clocks and a versatile manufacturer of many types of timepieces.

Chronometer Frodsham The Hydrographic Institute of the Navy has a Frodsham, the no.5013, on which is engraved Charles Frodsham 84 Strand London, where was already located the factory of Arnold. It's a chronometer to half seconds, with free escapement and compensated rocker arm, housed in a wooden box on gimbals

But the time required for making a timepiece ranged from three to two years and the costs were prohibitive, because the watchmaker was a lone and secretive inventor. Therefore these first timepieces were valuable tools for the exclusive use of government authorities and were only loaned to the great explorers-hydrographers during their journeys.

Chronometer Poole The Hydrographic Institute also has a timepiece J. Poole, No 5063, purchased in 1878 and used at important occasions, such as De Filippi's expedition to Himalaja , the hydrographic campaigns in the Red Sea and the Polar expedition of the "City of Milan". The prestigious John Poole factory was located in London, Fenchurch Street.

The mass production for general use, and then the solution to the hystorical problem for sailors, is due to the British John Arnold (1736-1799) and Thomas Earnshaw (1749-1829).

Arnold improved the innovations introduced by Le Roy, and had the intuition, unlike his predecessors, to establish a company in which make use of skilled workers (that, in turn, became watchmakers) for making parts, reserving to himself the mechanics of the instrument. In this way he, at the end of the eighteenth century, had produced a thousand timepieces at low cost, many of which were employed on board. At his death the company was continued by his son John Roger and, at his death in 1843, was taken over by Charles Frodsham.

Earnshaw is credited for having further improved the escapement and the rocker arm, making them roughly as we know them today.

Chronometer Poole
Another timepiece manufactured by John Poole is kept in the Galata Maritime Museum in Genoa; it was used at the end of the nineteenth century by Captain Henri d'Albertis on board of his cutter "The Corsair".
Chronometer McGregor
The astronomical observatory Giuseppe S. Vaiana in Palermo has the timepiece McGregor No 186, about 1868, kept in a walnut case, with hook closure, padded inside, with leather straps for transportation and holes for the screws.
Inside is the dark mahogany watch box, 17.5 x 17.5 x 19 cm, with handles and brass fittings. Outside, an ivory oval contained perhaps the name of the manufacturer. The upper face of the box can be opened, to read the watch through a glass window. The box also opens into two halves on a hinge like a book, to give access to the clock.
The latter is mounted on a gimbal that can be locked by means of a lever, in turn blocked by a knob screw. The watch can be easily reversed to recharge it with a key kept in a special slot in the box.
The dial is silver plated, has a diameter of 11.5 cm, with the hours in Roman numerals. The seconds are counted in a small eccentric dial, and a second upper dial indicates the charge status of the clock.
Chronometer Naviquartz Chronometer Naviquartz property of the Hydrographic Institute of the Navy.
The hands for minutes and hours are in steel, and those for the seconds and the charge status in burnished steel. It is signed
D. Mc Gregor & Co
Makers to the Admiralty

A few decades ago, the mechanical clock has been replaced by quartz, which maintains the traditional appearance, in its elegant mahogany box, while the movement has little in common with the clock of the past: the controlling element of time is represented by a quartz crystal placed in an oscillating circuit, whose high frequency stability ensures a very stable time base, regulating the movement of hands with an accuracy of few tenths of a second per day. The power supply is a battery and the charging interval is at least one year.

Another advantage is that the quartz clocks are insensitive to movement of the ship and to any type of noise. Moreover, when made as a control system, the timepiece can pulse a high number of clock repeaters located in different rooms on board, to ensure the correct timing to all guests of the ship.

By Paola Presciuttini