Negretti & Zambra Air Meter.

[Tweakie]

I wonder just how many of these were actually made ??
By act of parliament every mine in the UK had to have one also public buildings, prisons and hospitals were also required to have them.

Negretti & Zambra were just one of at least 6 different instrument manufacturers in the UK who produced these devices in their thousands yet, surprisingly, very few seem to have survived the passage of time.

I just could not resist purchasing this one for the princely sum of 50 pence.

Tweakie.

[andyf]

Can't be bad for the price of a bar of chocolate, Tweakie. But what does it actually measure - wind speed? And why on earth were they compulsory for public buildings?

N & Z were big instrument makers. I have one of their weather forecasters, like this example:
http://www.tooveys.com/lots.asp?WEBLOTID=203418&LOTID=1097
The dials are used to input things like which way the barometer is moving and the wind direction, and then a forecast shows up in a little window. About as accurate as any other weather prediction for the UK: hopeless.

Andy 

[Tweakie]

Can't be bad for the price of a bar of chocolate, Tweakie. But what does it actually measure - wind speed? And why on earth were they compulsory for public buildings?

Hi Andy,

This little device just measures airflow. It would be positioned in an entrance or doorway, the area of the opening measured and after a set time the reading taken and total airflow calculated.
 
In the days, long before Health and Safety, ISO16813 and HVAC etc. the main concern was, I think, the spread of Tuberculosis so an adequate change of air was considered necessary as a health precaution for all public buildings and measurements had to be taken at regular intervals and recorded in a log.

Tweakie.