A FEW weeks ago, I drove from the south of England to North Yorkshire via the A1. It was a Sunday and traffic levels were moderate, there being a welcome absence of heavy goods vehicles.

On two occasions, I was in a line of cars all moving smoothly, when suddenly someone at the head of the queue braked. Everyone behind that car was forced to brake somewhat unexpectedly but, happily, there were no accidents.

And the cause of the sudden braking? It was a speed camera. Drivers in the leading cars had noticed it and had braked accordingly, so we all trooped past the camera at a very sedate speed like naughty schoolchildren behaving because a teacher appears on the scene.

And, again like naughty schoolchildren, once the danger had passed we all gathered speed. That incident happened twice during my drive to Yorkshire, but there were no accidents.

But did those cameras really reduce our speed, and do they prevent accidents? Certainly we reduced our speed, but only while we were passing the cameras, and the effect of making so many motorists brake suddenly was likely to cause accidents.

I make reference to this because figures recently released by the Department of Transport show that, over the last three years, casualties increased at 743 speed camera locations. The department said it could not explain why.

Is it because motorists brake suddenly when approaching a camera and thus cause accidents?

The same report announced that in the financial year 2002-3, speed cameras generated an income of £68,872,320 and also admitted that some 245 of the existing cameras have failed to reduce road casualties.

One cannot wonder that so many motorists regard speed cameras as nothing more than tax collectors and experts now disagree as to the genuine merit of this kind of high-tech traffic control.

Many years ago, I attended a lecture by a senior police officer who specialised in traffic matters and he caused something of a furore among his audience by suggesting that high speed did not cause traffic accidents.

He said it merely aggravated them. High speed alone, he maintained, was not the cause of accidents; some other factor was invariably present, such as inattention by the driver, careless or even dangerous driving and possibly mechanical defects in the vehicle.

It has been suggested that, when the figures relating to speed cameras are published and discussed, they do not take any of those other contributory factors into account.

If a fatal accident occurs at the site of a camera, can it be said that death was due merely to speed or was there some other contributory factor, like inattention or careless driving? Faulty brakes perhaps?

One traffic expert reminded me that if a car is driven at 71mph along the motorway on a fine, dry, sunny day with no other vehicle in sight, it is breaking the speeding laws.

On the other hand, if it is driven at 70mph on the same road in dense fog, thick snow and with ice on the surface, it is not breaking the speeding laws. I know which driver I would prefer at the wheel.

Among the supporting evidence for speed cameras over the past three years is that there have been 100 fewer deaths at the sites of speed cameras.

I have no figures to tell me how many deaths still occur at those sites, or whether such deaths or serious injuries are caused by speeding. And do we know how many deaths or serious injuries at speed camera sites were actually caused by a vehicle travelling slower than the prevailing limit?

There is a lot more to be disclosed about the true value of speed cameras, whether or not they are merely tax-gathering machines. If they are generating yet another stealth tax, however, then this Labour government will retain them. It would seem that speeding motorists are doing their bit for the nation's economy.

Happily, I understand there are no fixed speed cameras in the police areas of either North Yorkshire or County Durham, but there are some within the territory of Cleveland Police. Income from their cameras for 2002-3 was £1,463,700.

A few weeks ago, we encountered a curious matter as we unfolded our sunshade umbrella after its winter storage in the garage.

When I opened it, I found two strange deposits within the folds, each attached to the fabric. The two deposits were almost identical.

At first glance, they looked like pieces of ridged chocolate cake with yellow icing in the hollows but when I looked closer, I realised this was not the case.

Each was about three inches long by an inch and a half wide and about half an inch thick.

The brownish bits, I discovered, consisted of earth which appeared to have been cemented by the saliva of some creature and formed into tiny building bricks.

Those bricks formed a series of small walls, so the complete objects had the appearance of a very miniature house without a roof, albeit with several rooms and doors.

There were five rooms in each little house. Inside each of the rooms was a yellow ball about the size of a garden pea with the consistency of fudge or perhaps butter icing or marzipan.

I think those balls were made of pollen, also mixed with saliva, and I think there would be an egg or grub inside each of them.

The little constructions were quite delicate and fell apart when I began to open the umbrella, but what had made them? I have never seen anything of this kind before and could find no suggestions in my various sources of reference.

I do not know when they were built in the folds of the umbrella, except that it was taken in for storage last autumn and opened in the late spring of this year.

I believe those fascinating little structures were the work of an insect of some kind, probably some species of bee or wasp, or perhaps a butterfly or moth.

Maybe one of our readers has encountered such things and can help solve this mystery?

Today is the feast day of St Mary, otherwise known as St Mary's Day, and there is an old Yorkshire saying which goes: "If it rains on St Mary, it will rain for four weeks."

The snag is that no-one can be sure which of the many saints called Mary is honoured today. Certainly, it is not the Virgin Mary because her principal feast day is on August 15.

Some other St Marys have their feast day in July, such as St Mary Goretti (July 9), St Mary-Magdalen Postel (July 16) and St Mary Magdalen (July 22). Other saints called Mary have their feast days at varying times of the year.

Following St Mary's Day, however, are the Dog Days. They begin on July 3 and continue until August 11.

Surprisingly they have little or nothing to do with dogs, but are more associated with the Dog Star, otherwise known as Sirius. This is the brightest star in the firmament in the constellation of the Big Dog, Alpha Canis Majoris.

The Dog Days are known as the days of great heat, probably the hottest time of the year. The ancient Romans called those hot weeks caniculares dies because they believed that the Dog Star rose with the sun during those weeks and added to the sun's heat.

Thus, in their opinion, the intense heat of that period was due to a combination of the heat generated by the sun and the Dog Star.

That is not the case because the Dog Star does not generate heat on Earth, nonetheless we have retained that ancient name for this period of extra warmth.

During the Dog Days there are several well-known dates which supposedly affect our weather. One of the best known is St Swithin's Day on July 15, and St James Day on July 25, but perhaps we should concentrate on the Dog Days while remembering this old saying: "Dog Days bright and clear, indicate a happy year; but when accompanied by rain, for better times our hopes are vain."