Oral Practice Box

All these texts should be carefully read and translated. Then you should be ready to share the main ideas and concepts relating to the texts below in English

Oral presentation 1

Fog Signals

Sound is conveyed in a very capricious way through the atmosphere and the following points should be borne in mind:

1. Fog signals are heard at greatly varying distances.

2. Under certain atmospheric conditions, if a fog signal is a combination of high and low tones, one of the tones may be inaudible.

3. There are occasionally areas around a station in which the fog signal is wholly inaudible.

4. Fog may exist a short distance from a station and not be observable from it, so that the signal may not be sounded.

5. Some fog signal emitters cannot be started immediately signs of fog are observed.

Mariners are therefore warned that fog signals should never be relied upon implicitly. Particular attention should be given to placing look-outs in positions in which the noises in the ship are least likely to interfere with the hearing of a fog signal; experience shows that through such a signal may not be heard from the deck or bridge when the engines are moving, it may be heard when the ship is stopped, or from a quiet position.

Fog signal emitters of all types vary greatly in power; reserve emitters are often especially weak.

Fog signals are mainly produced by the following types of emitters:

The diaphone uses compressed air and generally emits a powerful, low-pitched sound.

The horn uses compressed air or electricity to vibrate a diaphragm and exists in a variety of types which differ greatly in their sound and power.

The siren uses compressed air and exists in a variety of types, which differ considerably in their sound and power.

The reed uses compressed air and emits a weak, high-pitched sound; it is particularly weak when hand-operated.

The explosive emitter produces short reports by the firing of explosive charges.

The bell, the gong or the whistle may be operated by machinery, sounding a regular character; by hand, sounding a somewhat irregular character; or by wave action, sounding erratically.

Oral presentation 2

Navigational Charts

It is known that for many years Great Britain and Russia have been main chart suppliers in the world. A chart is one of the most important publications for safety of navigation. Parts of the sea or of the ocean are given in it with the indication of depth, character of ground, coastline, dangers and wrecks. There are such notions as: geographical elements and navigational elements. All these elements have special marks and symbols.

According to scale charts are subdivided into Ocean charts, General charts, Plans and Large Scale charts. The Natural Scale is the proportion, which any measurement on the chart bears to the actual distance.

There are three Projections: Mercator, Gnomonic and Stereographic. While reading charts we must know definite amount of conventional abbreviations and signs which are grouped under titles: the coastline, coastal features, topography, natural and artificial features, control points, units of measurement, adjectives – characteristics, harbours, buildings – as prominent marks, different objects, lights, buoys and beacons, radio and radar, fog signals, dangers, various limits, soundings, depth contours, quality of the bottom, tides and currents, principal foreign terms.

Every chart begins from the correction date; dimensions of the plate and also of chart datum as well as heights and drying heights are introduced. Figures on the land show the Heights in feet above High Water Springs. At the same time the datum to which the soundings are reduced true is the level of Mean Low Water Springs. The Datum is the level of the sea for places where there is no tide.

Charts are generally drawn on the True Meridian, if not, a True Meridian is given on the Chart. Longitudes are referred to the Meridian of True Meridian Greenwich. Direction shows us that all Bearings are true and are given from seaward. The Bearings are referred to the True Compass, and given in Degrees are reckoned clockwise from 000° (North to 359°). The Annual Change in Magnetic Variation is shown at certain positions on the curves. A positive (+) prefix denotes an annual increase, and negative (-) prefix – and annual decrease in the variation.

While working with charts it is necessary to pay due attention to cautions and notes. It is of common knowledge that charts are always published by the Hydrographer of the Navy, London.

Oral presentation 3