A friend of mine says hundreds of planets have been discovered in the last few years. Is he right? - J Anderson, Houghton-le-Spring.

I understand that, with the exception of the nine planets of our solar system, more than 50 planets were identified by astronomers in the late 1990s. They are known as Extra-Solar stars because they lie outside our solar system. In August of this year alone, ten were discovered orbiting distant stars. More strangely, in October, astronomers discovered 18 planet-like objects located many million miles away in the direction of Orion.

In your answer to last week's question on the 1771 flood you said something about the effect of flooding on the Tyne but not much about the Wear. I would also be interested to know what effect it had on the Tees and the Yorkshire rivers. Also, what was the actual cause of the flood? - W Hall, Bishop Auckland.

I have not found records to suggest that the Yorkshire rivers suffered on the same scale as the North-East rivers in 1771. The flooding was attributed to particularly heavy rainfall culminating in the flood of November 17. Some observers of the time claimed that although the rainfall was exceptionally heavy it could not have caused floods on that scale.

One source claimed that a "water spout broke" near the source of the three rivers and this caused the mass of floodwater. I am not certain what was meant by water spout, but the Tees and South Tyne do rise in the same area - both are fed by streams that rise on the slopes of Cross Fell in Cumbria. The Wear rises in western Durham, but is in the same general area.

The Wear was as badly affected as the Tyne and, in Durham City, the water rose eight feet ten inches higher than ever before. Many gardens and buildings in the city were destroyed, but remarkably no lives were lost in the city. Many houses in Chester-le-Street were destroyed along with nearby collieries. Carcasses of horses, cows and sheep were found later, strewn along the banks of Wear.

On the Tees, Stockton recorded its greatest ever flood and at Barnard Castle eight houses were destroyed after the Tees topped the bridge and took its course along a street. Land at the Yorkshire end of the bridge was swept away and people had to climb down a ladder attached to the bridge. One cellar occupied by a dyer in Barnard Castle was inundated by the Tees. He managed to escape in time but returned later to find his cloths had "attained a colour beyond the most sanguine expectations". He sent samples to London and did a roaring trade. In Yarm, where there was 15ft of water in the street, one woman and a child sat for 15 hours on the rooftop of a house waiting to be rescued.

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