Colaba Observatory[1][2] was an astronomical, timekeeping, geomagnetic and meteorological observatory located on the Island of Colaba, Mumbai (Bombay), India.
The Colaba Observatory[3] located in Bombay was built in 1826 by the East India Company for astronomical observations and time-keeping, with a purpose to provide support to British and other shipping which used Bombay as a port. The 165 year old Building served as office space for the Indian Institute of Geomagnetism. Geomagnetism and meteorological measurements were started here in 1841 by Arthur Bedford Orlebar, who was then Professor of Astronomy at Bombay’s Elphinstone College. Magnetic measurements during the period 1841–mid 1845 were intermittent; following 1845 they became bi-hourly, then hourly. In 1845 Charles Brooke devised a self-recording photographic magnetometer[4] with a light-source, a mirror for amplifying the magnet’s movement, and a drum of photographic paper. This system gradually replaced the older manual method of taking eye-observations through vertical microscope which scanned the ends of a magnetic needle; the magnetic needle itself was suspended by a bunch of silk fibers.
The new photographic drum method ensured continuous recording of geomagnetic elements, and rapidly gained use all over the world. It came to Colaba in 1871, when Charles Chambers (later to become F.R.S.) held the Directorship. Through his thorough examination of geomagnetic measurements at Colaba, and his masterly interpretation of the physics behind the phenomena, he brought great esteem to Colaba Observatory. After his untimely death in Feb. 1896, the mantle of Directorship fell on the shoulders of Dr. Nanabhoy Ardeshir Framji Moos, the first Indian to hold this position.
Dr. N. A. F. Moos was an able successor to Chambers. With an Engineering degree from Poona, and a higher degree in Science from Edinburgh in Scotland, he saw to the efficient functioning of Colaba Observatory, regular analysis and interpretation of the measurements, and the starting of seismological observations. In 1900, the existence of Colaba Observatory came under threat, when a decision was taken to electrify the fleet of horse drawn trams then existing in Bombay for public transport. The electric trams by generating electromagnetic noise, would have vitiated the data from the Colaba magnetic observatory.
The credit of selecting the alternate site of Alibag, located about 30 km to the south-east of Bombay as the crow flies goes to Dr. Moos. Alibag was located “far enough from Bombay to be free from the threatened electromagnetic noise, and yet near enough to retain the same geomagnetic characteristics”–these aspects were checked out carefully over a 2 year period 1904-1906, and then only was recording at Colaba discontinued, and the electric tram service started in Bombay. The entire building is made of hand-picked, non magnetic, Porbandar sandstone, and magnetic recording is carried on in a room built with such good insulation, that the variation in temperature within, even today, is just 10°C over an entire day.
Of the entire Colaba - Alibag data, the French geomagnetician Pierre Noel Mayaud, had the following to say in 1973:
“Finally, the (magnetic) records of Colaba and Alibag were found to form a beautiful series, beginning in 1871, and making up perhaps, the most complete collection of records in the world. Their quality and especially their regularity were particularly impressive, even in comparison with the Kew and Melbourne records”.
Moos retired in 1919 after leading the Colaba-Alibag Observatories to worldwide renown. In 1910 he summarized the main findings from 50 years of geomagnetic measurement at the Colaba-Alibag Observatory over 1846-1905, in two volumes titled “Magnetic observations made at the Government Observatory, Bombay for the period 1846-1905. Parts I. and II." Of these volumes and of Colaba-Alibag’s performance as a Geomagnetic Observatory, J.A. Fleming, a pioneer in Terrestrial Magnetism and Electricity, had the following to say in 1954:
"The Golden Jubilee of the foundation of the Magnetic Observatory at Alibag (Mumbai), is a historic one in the field of Geomagnetism, and marks the long established application of India in an unparalleled series of magnetic recording of the phenomena, and publication of interpretative discussions of the accumulated data, as prepared under the direction of India’s foremost investigator (N.A.F. Moos) in the two large volumes.
Despite over 1500 selected references in the field of geomagnetic research, Volume 3 of the Physics-of-the-Earth Series of the United States National Research Council, there is none which exhibits so wide and varied and intensive coverage of all the geomagnetic problems in the early 20th century."
Of Moos, the Director who followed, Prof. K. R. Ramanathan (later to head the Physical Research Laboratory, Ahmedabad), said:
“He was an ideal head of the observatory, always taking a deep interest in the welfare of his staff, and being held by them in great affection and esteem”.
Over the year 1919–1971, 17 Directors steered the Colaba-Alibag Observatories through avenues of meticulous and uninterrupted geomagnetic recordings, regular publishing of the data, and discussion of observations in scientific research journals.
In 1971, a momentous change occurred with the conversion of the Colaba-Alibag Observatories, into an autonomous research organisation called the Indian Institute of Geomagnetism. Till then the Colaba-Alibag Observatories were part of the Indian Meteorological Department. Its headquarters continued to be in Mumbai, in the sturdy 1826 building constructed by John Curin, Astronomer for the East India Company. The first Director of the Indian Institute of Geomagnetism over 1971–1979 was Prof. B. N. Bhargava. Prof. R. G. Rastogi was the next Director over 1980-1989.
During the IGY-IGC years of 1957–1959, Prof. K. R. Ramanathan (a past Director of Colaba-Alibag), strongly advocated the setting up of magnetic observatories to examine the equatorial electrojet. The TRIVANDRUM and ANNAMALAINAGAR observatories were set up in Nov. 1957, and were tended in their infancy, first under the Directorship of Mr. S. L. Malurkar, and then under Prof. P. R. Pisharoty.
Eighteen years elapsed before the need for further observatories along 75°E longitude meridian was felt, to serve the needs of the USSR sponsored "Project Geomagnetic Meridian". Ujjain and Jaipur were consequently set up in July 1975, as also Shillong at 92°E longitude. In May 1977, Gulmarg, located very near the focus of the Sq. current system was started. In May 1991, the ninth observatory was started at Nagpur and then the observatories Vishakhapatnam, Pondicherry and Tirunelveli followed. Apart from these, a temporary station was run in the Andaman Islands in 1974, as support for the ONGC (Oil and Natural Gas Commission of India) in petroleum prospecting. Since 1979, an array of Gough-Reitzel magnetometers has operated at various sites in India, for studies of the Earth’s internal structure by examining electromagnetic induction within the earth. The Indian Institute of Geomagnetism thus operates Ten magnetic observatories.