Mr B. Martin's Experiments on Island Crystal, 149 
materials as those formerly described, and drawn over them and 
the drawers ; a pair of strong boots, with nails or iron on the 
heels ; a warm winter waistcoat, and a second neckcloth ; pair of 
long and wide cloth small-clothes, covering the boots and part 
of the waistcoat ; a cloth coat, with short flaps ; and a spencer of 
the same, go over the whole. A winter cap, lined with fur, and 
provided with ear-lappets, is the ornament for the head ; and a 
pair of gloves of similar materials, is certainly suited to the sea- 
son of the year. 
“ This is a comfortable dress, and proof against cold, rain and 
wind.” 
( To be continued.) 
Art. XXIII.— Historical Account of Discoveries respecting 
the Double Refraction and the Polarisation of Light. (Conti- 
nued from Vol. IV. p. 130.) 
Period III .—Containing the Investigations of Beccaria , 
Martin , Haiiy , Wollaston, and La Place.. 
Such of our readers as have taken an interest in the history of 
the Polarisation of Light, must have ascribed to negligence the 
delay which has taken place in the progress of this series of papers. 
Having arrived at the^period which embraces the experiments of 
Benjamin Martin, we were desirous of obtaining copies of the 
Essays which he published on this subject ; but with all our di- 
ligence we were not able, on account of their great rarity, 
even to obtain a sight of them. Through the kindness, however, 
of Mr William Jones, optical and philosophical instrument 
maker in London, who has transmitted to us copies of both Mr 
Martin’s Essays on this subject, we are now able to resume our 
labours. As these pamphlets are extremely rare and curious, 
we have thought it better to reprint then* entirely, than to lay 
before our readers merely an abstract of them. 
d 
