The IET Archives has just received back from conservators 4 volumes of pamphlets from the Professor Silvanus P Thompson collection of pamphlets. That collection comprises many hundreds of volumes of pamphlets organised by subject. Each volume, in addition to holding pamphlets, often contains trade catalogues and letters, typically correspondence with the author of a pamphlet. Most of the volumes are in quite poor condition and need to be conserved before they can be catalogued and studied.

The first conserved volume has the title ‘hailstones’, and the above image shows the cover of one of the pamphlets, an 1882 publication written by Theodore Schwedoff, titled in French ‘sur l’origine de la grêle’ or in English, ‘on the origins of hail’ (more on Schwedoff later). Many of the pamphlets contain lovely illustrations of hail or hail producing clouds such as the two images below. The first image is of a hail cloud of June 1877 seen from Geneva.



Some of the pamphlets also discuss and illustrate the track of specific hailstorms. The first image below shows the path and incidences of heavy hail from hail clouds near Lake Geneva in July 1875.


Newly discovered letters

This volume of pamphlets also contains a significant number of letters mostly dating to 1882, the year of the Schwedoff pamphlet shown above. The theory about hail expounded in that pamphlet was apparently a new theory, and amongst the items in the volume on hail is a 23-page manuscript written by S P Thompson titled, ‘on Schwedoff’s theory of hail’. The paper begins, “so novel a theory as that propounded by Professor Schwedoff on the origin of hail naturally excites the question, can it possibly be true?”

The volume includes two letters written in French by Schwedoff, Professor at the University of Odessa, and sent to Thompson which discusses his theory (the envelope for one of the letters is shown below).


Thompson’s correspondence with other scientists and meteorologists on the subject of hail is also reflected in the letters. There is a letter in the volume from A S Hershel, dated 20 August 1882 where Hershel agrees to joining ‘the Hailstorm Committee’ [probably a British Association committee], and comments that Schwedoff is a, “trustworthy authority I believe and an original writer, in his theories, of a work on comets, who has probably digested his information very thoroughly and well.” Professor Alexander Stewart Hershel (1836-1907) was a British astronomer who did pioneering work in meteor spectroscopy. He also worked on identifying comets as the source of meteor showers.


Other letter writers whose letters can be found in the volume on hail include Maxwell Henry Close (1822-1903) who was an Irish Church of Ireland clergyman and geologist who contributed to the preservation of the Irish Language. Close was also a Treasurer of the Royal Irish Academy and President in 1878 of the Royal Geographical Society of Ireland. Close’s letter, on Royal Irish Academy headed paper (30 August 1882,) mentions Thompson’s paper to the British Association about ‘cosmical (sic) masses of ice’ and talks of meteorites and examples of meteorites reaching the earth.


There is also a series of correspondence between Thompson and the British Meteorologist George James Symons (1838-1900), who was a prominent member of various committees appointed by the British Association. Symons was also a Fellow of the Royal Society and acted as Chairman of its committee on the eruption of Krakatoa in 1883.


The hailstones volume of pamphlets (archive reference SPT/P/I/144) will be catalogued at item level during 2017 and will then be available to consult at the IET Archive Centre by appointment.