Six's Thermometer

The thermometer on the right is a special one for recording maximum and minimum temperatures. All Six's thermometers have one long 'U' shaped tube. This can be clearly seen in the image further down the page.

There are two bulbs of alcohol at the top of the tube. These can be seen on this thermometer. These expand or contract as the temperature changes. They then push round the indicator liquid to show the temperature. This example has no mercury, and is therefore safer.

You get to see the temperature twice, it should show the same temperature on both scales. Both Celsius scales show 19 °C.

The Marker Pins

So that the Maximum (hottest) and Minimum (coldest) temperatures can keep be recorded there are two small steel pins.
When the temperature rises, the marker 'pin' in the right hand column is pushed upwards. It will stay there until you reset it. You read the bottom of the 'pin'. This example is 28°C.
When the temperature falls, the marker in the left hand column will be pushed upwards to show the minimum temperature. Read the 'pin' at the bottom point. This example is 16°C. See more about reading the scales below.

Reading the Scales

The close-up of a part of the scales on the right shows how they are reversed.
The right hand scale, for the maximum temperature, is the 'normal' way up. The larger numbers are at the top. Below the zero are the minus numbers (shown here in red).
The left hand scale, for recording the minimum temperatures, is reversed. The larger numbers are at the bottom. The minus numbers are above the zero (see the plus and minus signs).
When reading the temperatures that the pins were left at, always start at the zero and look carefully whether the number should be a positive number or a negative number.

Resetting a Six's Thermometer

There are different ways of resetting the thermometer so that the pins move back to the current temperature.This is done at 09.00 GMT in the United Kingdom. Elsewhere is is 09.00 local time. Some thermometers simply have a little magnet which is used to pull the pins back down.
The video clip on the right shows a device where a magnetic strip stops the pins from falling down when the temperature changes. When the button is turned the magnet is pushed away from the pins and gravity can pull the pins down to the current temperature. If you look closely you will see the pins going down.

On other Six's thermometers when a button is pressed a similar thing happens. See a video of resetting by pressing a button.

Caring for a Six's Thermometer

As with most weather instruments you need to treat a Six's thermometer very carefully. There are glass parts which can be easily broken. If any instrument gets broken seek advice from an adult immediately.
When you buy a Six's thermometer make sure that the indicator liquid does not have any gaps in it. Also check that the pins are not buried in the indicator liquid.
Although many Six's thermometers have mercury for the indicator liquid there are ones without this poisonous metal. The one on the right has mercury in it. You can see the shiny silver colour. It may be better to purchase one without mercury. Search the internet for a supplier.

James Six (1731 - 1793)

This is called a Six's thermometer because it was invented by a man called James Six.He was born in Canterbury and did some scientific experiments in the cathedral. The picture on the right shows this beautiful cathedral.
As part of his science experiments he wanted to record the weather and did not want to keep getting up in the night to take readings. For this reason he invented this sort of maximum and minimum thermometer.