The issue of climate change is a subject that is front and centre of the debate about how our society should move forward to secure our future. There are records, models and forecasts (some more reliable than others) that feed into the discussion.
So it is interesting to look at a weather record, compiled in the 18th century, by an English spectacle maker, James Ayscough, better known for designing spectacles with eponymous double-hinged sides. He also produced a range of scientific and optical instruments, which he no doubt employed in taking his meteorological measurements.
Ayscough was clearly well-regarded by his optical peers as he was elected Master of the Worshipful Company of Spectacle Makers (WCSM) in 1752.
James Ayscough was born in Wiltshire, the son of a clergyman, in 1720 and at the age of 23 began a five-year apprenticeship under the optician James Mann. This was a good position to land as Mann had been Master of the WCSM for two years during 1735-6, following in the footsteps of his father, James Mann senior, who was WCSM Master in 1716 and who had studied under Sir Isaac Newton.
Unsurprisingly, since both Manns were expert microscope makers, Ayscough too became known for his microscopes.
Eventually he branched out on his own, taking premises in Ludgate Street, near St Paul’s Cathedral, under the sign of the ‘Great Golden Spectacles’.
His trade card announces that he ‘Makes and sells (wholesale and retail) SPECTACLES and READING-GLASSES’ and also ‘CONCAVES for short-sighted persons’. It also advertises a variety of optical instruments as well as maps and globes. A later trade card puts his address at 33 Ludgate Street, now under the sign of the ‘Great Golden Spectacles and Quadrant’.
Here he prefaces his list of products with the line, ‘The Original Shop for superfine Crown-Glass SPECTACLES’ and later points out that his lenses are ‘set in neat and commodious Frames, some of which are contrived to press neither on the Nose nor the Temples.’
Frames with sides, as opposed to ‘nose spectacles’ only began to appear in the 18th century and are generally credited as being developed by London optician, Edward Scarlett (another WCSM Master).
Loops at the ends were later added, through which a ribbon could be threaded to help keep the spectacles from falling off. Ayscough’s innovation was the double-hinged side that now bears his name (pictured below).
These sides, hinged to the front and folding in the middle, Ayscough wrote, ‘obviate all the objections made to the common spring spectacles, as they neither press upon the nose nor the temples; the complaint against these being the pressure they cause on that place, which stops the circulation of the blood, and thereby occasions to many people violent head-aches.’
Coloured glass
Ayscough also advertised that he supplied lenses in white, green and blue glass ‘ground after the truest Method’. In fact, he recommended green or blue lenses for certain vision problems.
In a pamphlet entitled A Short Account of the Nature and Uses of Spectacles he explained: ‘For the Colour of Glass, the whitest has generally been made use of for spectacles, but I am inclin’d on many Accounts to prefer another Sort before it… for the common white Glass gives an offensive glaring Light… insomuch that some advise green or blue glass, tho’ it tinge every Object with its own Colour…
That which I recommend is… a little ting’d with Blue, it takes off the glaring Light from the Paper, and renders every Object so easy and pleasant that the tenderest Eye may thro’ it view any thing intently without Pain.’ Something that wearers of the old pale blue Crookes Alpha tint would attest to.
In addition to his optical research Ayscough pursued a meteorological interest. The Gentleman’s Magazine had published weather information as an addendum to its daily stock market report from January 1747.
Ayscough began contributing his own daily weather data to every monthly issue in February 1755, which consisted of two temperature readings, one in early afternoon and one late in the evening; a barometric pressure reading; and a brief summary of the day’s weather.
His barometric readings were given initially to a 10th of an inch accuracy but soon were recorded to 100th of an inch, suggesting that he may have switched from using the magazine’s own instrument to one of his own.
For context, there were other contemporary journals, such as The London Chronicle and The Universal Magazine, that published their own weather data. There were also other individuals and institutions around the country taking meteorological measurements.
Perhaps the most notable of these are the recordings begun in 1659 as monthly readings, continuing from 1772 as daily readings, in an approximately triangular area bounded by Bristol, Manchester and London, which were collated into a series known as the Central England Temperature (CET) record by Professor Gordon Manley from 1953.
The readings continue to this day, now maintained by the Hadley Centre for Climate Science in Exeter, a branch of the Meteorological Office, constituting the longest instrumental temperature record in the world. There is some uncertainty about the accuracy of some of the early readings, but then there are some doubts regarding the veracity of the Met Office’s input too.
They started making somewhat arbitrary adjustments to the temperature recordings in 1974 (and even they cannot explain why that date was chosen), and the weather stations used to collect data have significant questions to answer about changes in the environments in which they are sited (eg new roads and buildings nearby; shielding from north winds). A penny for the thoughts of James Ayscough, precision instrument maker.
Meteorological influence
Ayscough’s contributions to The Gentleman’s Magazine inspired one George Smith, who lived near Carlisle, to contribute for comparison a similar record for Cumberland.
An anonymous correspondent from Hampstead went a step further in The London Chronicle. He saw a value in looking at averages of temperatures over time and using them to predict future temperatures; quite possibly the first use of a statistical method for weather forecasting.
In his column, he suggested that by ‘taking the medium of heat in each fortnight for a course of years, we shall be able to fix the medium naturally to be expected.’ Ayscough’s data began appearing in The Gentleman’s Magazine just as another contributor was ending a four-year stint publishing there his own climate statistics.
John Fothergill, a doctor and amateur botanist from a Quaker family, sent in monthly reports to the magazine during 1751-55, which included temperature and pressure readings and medical assessments of the illnesses active among his patients from his base in Lombard Street in the City of London.
Incidentally, among his other medical writings, he provided a wonderfully vivid description of visual aura experienced during migraine: ‘A singular kind of glimmering in the sight, objects swiftly changing their apparent position, and surrounded with luminous angles, like those of a fortification.’
Ayscough’s meteorological contributions to The Gentleman’s Magazine continued until his death in 1759, the last entry being on August 23 at Clerkenwell, London. He is certainly best known for his double-hinged frame sides and is still recognised for the quality of his microscopes. He is less known for his weather observations, but their accuracy speaks to his skill as an instrument maker.
Ayscough also played a role in the popularisation of achromatic lenses, which he fitted into some of his telescopes. The inventor of the achromatic doublet was barrister and mathematician, Chester Moor Hall. Not being a lens grinder, but wanting to protect his secret, he commissioned Edward Scarlett and James Mann to each produce one component of the doublet.
Unfortunately for him, they both subcontracted their work to one George Bass. Hall, uninterested in patenting the invention, gave the lens to Ayscough to popularise; whose claim to fame here is as the first person to use the term ‘achromatic’, the word appearing in his last shop leaflet.
Strangely there was not much enthusiasm for the lens at that time, but some time later, an amateur optician who had been struggling with the problem of constructing an achromatic lens came into contact with Bass, who told him of the two component lenses that he had been contracted to make. This optician took the idea, patented it and John Dollond made his fortune.
James Ayscough: spectacle maker, instrument maker, meteorologist, achromatic lens marketer. His promotion in his written works, and use of coloured lenses, both blue and green, to mitigate the harshness of ambient light has led some authorities to cite these coloured spectacles as the precursors of sunglasses. His meteorological observations would have made him perfectly placed to advise when to wear them.
- David Baker is an independent optometrist.
