Thus was named the radiator thermometer fitted to Morris cars from the 1st September 1925. Morris Motors Ltd also described it as a ‘day and night reading radiator thermometer’ when first introduced for the 1926 season Morris Oxford and Cowley models.

It was, however, not the first form of radiator temperature gauge to be fitted as standard by Morris. For the 1924 and 1925 seasons Morris Motors Ltd had been including a device supplied by the Benjamin Electric Co Ltd, Brantwood Works, in Tottenham, North London called the Boyce Mote-Meter and paying a royalty on every one fitted. The Boyce Mote-Meter, like a number of parts used on the early Bullnose cars, came originally from the United States having been invented by one Harrison Hurlbert Boyce of Jerico, Long Island in 1912. The Boyce Mote-Meter was fitted to the radiator cap with the indicating side of the dial facing the windscreen, enabling the driver to monitor the cooling water temperature. Within the instrument was a glass tube which extended down to the stem and which contained a red fluid which, as it expanded with heat, appeared as a red ribbon travelling upwards through markings indicating ‘Cool Motor’, ‘Summer Average’, and ‘Danger Steam’. It was recommended that the internal combustion engine ran best and most efficiently when the temperature of the cooling water as it left the engine jacket was at, or slightly over, 200° F (about 93°C). From 1921 onwards it was fitted to something like 390,000 British motor cars including 72,651 Morris vehicles, resulting in the payment of a substantial sum in royalties.

PICTURE: Early example of the original Calometer advertised by the Wilmot Manufacturing Co. Ltd. in 1926. Note the spelling of “CALOMETER”.

Meanwhile, a Mr T. H. Whiting of Edgbaston, who was in charge of the tool room at the Wilmot Manufacturing Co Ltd of Birmingham, was working on a design for a radiator thermometer to be called Calometer. After three months patient hard work, with the assistance of C. L. Breeden (who later became a partner in the business which changed name to Wilmot-Breeden) and with further help from the Works Manager, Mr Wessen, the finished prototypes were accepted by the patents agent. The principle of the Calometer was based on two strips of dissimilar metals mounted lengthwise in a vertical tube and attached at one end to a toothed quadrant. When the temperature rises the two strips of metal expand differently and tend to straighten with the result that the quadrant moves and the pointer turns.

William Morris was introduced to the new instrument when C. L. Breeden gave him a prototype for evaluation. The resulting tests, made by William Morris on a trial run through France, were satisfactory and, no doubt with an eye to saving on the royalty payments being paid for use of the Boyce version, Morris placed an order with Wilmot Manufacturing Co for 25,000 units per year.

In the construction of the original Calometers, parts of the body were turned out of delta brass rod, then milled, filed, drilled and tapped, before finally being brazed to the threaded neck. The more delicate components such as the toothed quadrant, pivot, black pointer, etc were assembled by operators trained by T. H. Whiting when a branch works was set up at Tysley. He and Mr Wessen being responsible for the layout of the new factory. In 1925 the Calometer was patented in the names of C. L. Breeden and H. W. F. Ireland. Mr Whiting was rewarded with the sum of £5 by Mr Breeden and when T. H. Whiting died at a grand old age in the late seventies he still possessed one of the first six Calometers that were manufactured. This has now passed into the hands of his son Gordon B. Whiting of Coventry for safekeeping.

The Calometers were fitted as standard equipment on all Morris models from the 1st September 1925 and the following month ‘The Motor’ published the results of tests they had undertaken on the Calometer. To ensure that the instrument did all that was claimed for it, the testers made the engine of the test-car boil by fitting a radiator muff, but everything was to their satisfaction and much was made of the fact that the instrument could be read both during the daylight, and by means of the illumination of approaching cars, at night. However, Boyce were not at all pleased to see their royalties dry up, particularly as other motor manufacturers such as Austin and Clyno, were now fitting the Calometer to their cars. Boyce sued Morris for patent infringement and the case was heard before Mr Justice Astburn in the Chancery Division of the High Court in November and December 1926. The case lasted ten days during which time the lawyers for Morris alleged that the Boyce patent was invalid by reasons of prior use, wherein thermometers placed in radiators of cars had been used for testing the performance of cars and settling their design. Further, it was alleged that the invention was not useful because certain advantages alleged by the patentee were not obtained. The court held that the device gave real and practical advantage in communicating to the driver at the right moment the existence of danger and there was real exercise in the inventive faculty. The alleged prior use was held by the court to be at the most a mere casual, accidental or incidental use in the course of a completely different investigation. Morris Motors Ltd had infringed the Boyce patent – the finding that was upheld by the Court of Appeal after a six day hearing in February and March the following year.

Morris was poorer by not less than £50,000 in damages and by way of legal costs, yet he continued to fit the Calometer to his cars, having found a way around the court’s findings. Boyce’s patent had described their device as ‘… comprising a thermometer, the heat responsive element of which is exposed to the temperature conditions prevailing within the so called air space immediately above the normal surface level of the liquid.’ By increasing the stem length of the Calometer, it was then the temperature of the liquid itself and not the temperature of the air space above it that was being monitored. It can be assumed that as a new patent was taken out for the Calometer in 1927 by C. L. Breeden and H. W. F. Ireland, it was to cover these changes.

It could well have been the shadow of the legal costs involved with the Boyce case that prompted a change in the spelling of ‘Calometer’ to include the letter ‘r’ and become ‘Calormeter’ in 1927. On the market at the time was a device made by The Autovac Manufacturing Co Ltd of Heaton Norris, Stockport which, while having no thermal function, was called the ‘Galometer’. To avoid confusion with this instrument, which measured fuel consumption in conjunction with the Autovac, Wilmot Manufacturing Co Ltd decided to include the additional letter.

In conjunction with the Calometer being fitted to the 1926 models, Morris also fitted a device to the 13.9hp Oxford during that season called the ‘Thermet’. Positioned in the hose between the radiator and the cylinder head, the Thermet operated as a valve which remained closed until a pre-determined heat was attained and then opened to allow the normal circulation of water. There is something of a mystery about the supplier of the Thermet, for initially Morris publications listed a firm called Johnson Motor Co Ltd of 177 Clifton Road, Aston, Birmingham, as the manufacturer. Whether Johnson’s were taken over by S. Smith & Sons (MA) Ltd is open to conjecture, but four months after the introduction of the 1926 Morris Oxford, it was being listed and advertised as the Smith’s Thermet.

Morris continued to fit the Calormeter to almost all their models right through to mid-1935 when the new Series models were introduced. Until about 1930, when chromium plating was generally introduced, these instruments were finished in nickel plate. The Calormeter varied in design from the smaller round ‘Prince’ or Baby model on the Morris Minor to the semi-octagon ‘Emperor’ shape fitted to the larger Isis, Oxford and Major. Other motor manufacturers fitted the Calormeter as standard, or were catered for by Wilmot-Breeden. These marques included Austin, Ford, Triumph, Wolseley, Jowett, Lanchester, M.G. and Standard. Some variations being specifically designed, such as the imposing version with the additional ornamentation of a Roman Standard for the Standard Motor Company Ltd and the single wing fitment for the Wolseley Hornet and Viper.


EA 125 17786 Early Oxford/Cowley (?)
19093 VICEROY 19092 SPEED (large) Morris Oxford/Cowley Chas. 57101 to 341406
36138 PRINCE or Baby Model 36139 SPEED (small) Morris Minor SV inc. vans Chas. SV101 to SV5535.
Morris Minor OHV, Family Eight, Chas. M101 to M34699
19496 ‘PRESIDENT’ Morris Cowley/Oxford. Chas. 341407 onward
40380 EMPEROR 40381 SPEED (large) Morris Major Six. Chas. MJ101 to MJ4125
Morris Oxford Six. Chas. LA101 to LA23746
Morris Isis Six. Chas. IS101 to IS4039
45759 REGENT 19496 ‘PRESIDENT’ Morris Minor SV inc vans, Chas. SV5536 on.
Morris Minor LWB SV, Chas. 20301 on.
Morris Minor OHV & Family Eight, Chas. M34700 on.
Morris Ten Six 1934/35, Chas. 14281 on.
(not fitted to Ten-Six Special)
Morris Ten-Four 1933/35, Chas. 101 on.
Morris Cowley Four & Cowley Six, Chas. 501 on.
Morris Major Six, Chas. MJ4126 on.
Morris Oxford Six, Chas. LA23747 on.
Morris Isis Six, Chas. IS4040 on.
Morris ’25’, Chas. 5611 on.
‘NO WINGS’ Morris 8/10 cwt van, Chas. 382398 on.

Harry Edwards

Bibliography and Photographic credits
The Journal of the Morris Register, Spring 1989, Vol.12 No.5