The chemical and physical work done at sea is chiefly the collection of samples of water and the observation of temperature. Water from any moderate depth is collected by lashing a bottle to the sounding-line and lowering it to the proper point; the stopper is then pulled out by a cord and the bottle allowed to fill. The water in the bottle is not changed in its ascent, as the mouth is narrow and it always hangs vertically. When the sea is rough or the depth is great, it is necessary to employ some other means. The ‘slip-water-bottle’ is convenient for most purposes. It consists of a brass disc covered with india-rubber, and supporting a central column to which the line is attached. This is lowered to the required depth, and then a hollow brass cylinder, open below, but closed above except for a hole that just allows the line to pass, is allowed to slip down the line. The base of the cylinder strikes on the rubber-covered disc, and securely incloses a sample of the water, which is run off by a stop-cock into a bottle after the whole has been hauled on board. The water must always be brought to the laboratory in stoppered bottles, which are entirely filled, and have had the stoppers tied down from the moment of collecting.
The temperature of surface-water is usually taken by drawing a bucketful and placing an ordinary bath-thermometer in it for a few minutes. The precautions of hanging the thermometer in the centre of the bucket and placing it in the shade must be observed. Temperature at greater depths may be observed in several ways. Three methods have been tried at the Marine Station. The first is by means of a ‘cistern-thermometer,’ used by the late Sir Robert Christison for ascertaining the temperature of the water in the deep Scottish lochs, which was presented to the Station by Sir Alexander Christison. It consists of a thermometer, the bulb of which is in the centre of a conical copper vessel capable of containing about five pints. When this is lowered into the sea, the water passes through the instrument; but on hauling up, the valves on the upper side are closed, and it is brought on board full of water from the greatest depth it had reached. Experiment shows that the water has not had time to change its temperature in the few minutes that elapse between collecting it and reading the thermometer. A more common instrument, though one not found so suitable for use in shallow water, is the Miller-Casella thermometer, the form chiefly employed on the Challenger. It is a self-registering thermometer with a maximum and minimum arm, which register the highest and lowest temperatures met with in each immersion. As the temperature of the sea almost invariably decreases with increase of depth, the lowest temperature is considered to be that of the lowest point reached.
The third form of thermometer has been found the most convenient, and, with some modification, the best for the purposes of the Station. It is Negretti and Zambra’s deep-sea thermometer, and its principle is that when the temperature of the water is attained by the thermometer the instrument is made to turn over; the mercury column always breaks at the same point, a contraction near the bulb; the part which had been beyond the bulb remaining in the inverted tube, which is graduated so as to show the temperature at the moment of inversion. Its great advantage is that no subsequent change of temperature affects the instrument until it is set again. Its great defect is that it is difficult to be sure when it has turned over. The simple and ingenious inverting mechanism of Magnaghi is hardly trustworthy; but an improvement has been effected, in consequence of the experience gained at the Scottish Station, which makes the turning of the thermometer, or of any number of thermometers on the same line, a matter of certainty.
The transparency of the water is measured roughly by noting the depth to which a large white disc continues visible when immersed. In the course of a trip from Grangemouth to the Isle of May, the colour of the water was observed to vary from dirty yellow to clear blue-green; and the disc, at first visible only three feet below the surface, was seen at a depth of six feet at Inchgarvie, at fifteen feet off Inchkeith, and at no less than sixty feet a little east of the May. Although the water of the upper reaches of the firth has been rendered muddy by the admixture of river-water, that at the May Island remains beautifully clear.
The routine-work of a biological and chemical laboratory is not of much interest to most people. For every day of collecting, with its fresh sea-air and new sea-sights, there must be several spent on the Ark in preserving the specimens, pressing plants, dissecting, mounting microscopic objects, observing densities, analysing water, calculating results, and such things; and all this work does not always tend to preserve an odourless atmosphere.
It is not intended that the Marine Station shall long continue of its present small dimensions. The experiment, so far as it has gone, has been so successful that it is now proposed to erect a large house on shore near the quarry, where there will be commodious laboratories, large aquaria, and rooms for the accommodation of the workers. In the meantime, Mr Irvine of Royston has generously given the use of an old manufactory which stands close to the sea beside the quarry. It was formerly used as a tannery, and so contains a number of large water-tight tanks built in the ground. There is a steam pumping-engine; and a very simple modification of the existing pipes will secure the supply of abundance of sea-water. The tanks will be used for experiments on fish-breeding; and the buildings in the works can be employed as laboratories without much alteration.
The Marine Station is intended to be a centre from which branches will extend to other parts of the country. It is in contemplation to erect a permanent marine observatory on the Clyde; and there will also be a portable station, probably a floating laboratory on the plan of the Ark, which can be taken to any part of the coast where it is desirable to make an extended series of observations.
The Granton Station is, with the exception of an annual grant of three hundred pounds from the Scottish Meteorological Society, entirely supported by voluntary subscription; and the heartiness with which the appeals to the public have been responded to by donations of money, apparatus, and material, shows how thoroughly the people of Scotland realise the importance of the work which is being done. The Government Grant Committee of the London Royal Society has made certain allowances to the members of the scientific staff for special researches; but this is not in any sense a government endowment of the Station, the Treasury having definitely refused to give any money for such a purpose. Although government support is an extremely desirable thing, the willing aid of an enlightened public is still better, and the Scottish Marine Station at Granton has this aid.[1]