Apbil, 1903.] 



KNOWLEDGE, 



91 



|)oiiit of the eastern apse ; and carries the altitude to 

 160 feet — a round number, and a multiple of the number 

 40, so frequently met with in Byzantine architecture. It 

 was evidently for the sake oi the "aerial " cupola and of 

 the cornice that the idea of a continuous pendentive dome 



Fig. 8.— Capital of one of the Great Columns of the Nave, 

 with the Monogram of Justinian. 



was rejected. Under the existing circumstances, however, 

 such aerialty was not to be obtained in connection with a 

 flat dome, except at a tremendous cost of solidity. The 

 thrust exerted by the over-daring cupola of Anthemius on 

 the piers and semi-domes was so overwhelming that a 

 catastrophe through failure of some point of the supports 

 co\ild not long be averted. 



It is generally believed that Paul the Silentiary does 

 not mention any mosaic images on th*' vaults in 5tio. 

 Such, however, is not the writer's impression. The poet's 

 description of the dome has not been preserved intact ; 

 there is a lacuna in the Greek text from verse 80 to 

 verse 92, and, amid the drhris of words, overlooked by all 

 authors, we find : — 



90. ...... lyhtOi xu'kXou 



91. . \{n)<f>(S . I'l'^piL (Taiixni 



92. ii<j>poup xoVftoio tTauiri'jp, 

 that is, in English : — 



" In a circle — mosaic — in order to save — always well 

 guard 1'^°}*— tlie Saviour of the World." 



The Painter'g Manual recommended to " draw ncai' the 

 summit of the cupola a circle of different colours. . . . 



In the centre represent Christ with the Gospel, and this 

 inscription : ' Jesus Christ the Almighty.' " And it is 

 evident that the great analogy between this description 

 and the few remnants from the broken verses constitutes 

 a positive proof of the important fact that the Pantocrator 

 has adorned, from the very onset, that most genuine 

 representation of the flattened vault of heaven. 

 (To be concluded.) 



* The remnant ei^itpovp seemtj to be some combination of afi, 

 " always," and .^povprfio " I guard." The adjective, in poetic language, 

 is d«t</>povpo< or ati^ptniftifTot, . 



Conducted bij M. I. Cross. 



NOTES ON THE COLLECTION, EXAMINATION AND 

 MOUNTING OF MOSSES AND LIVERWORTS. 

 By T. H. Rdssell. 

 (Continued from page IQ.) 

 As far as my acquaintance with glycerine jelly goes — and it 

 is one of a good many years' standing— the great objection to 

 its use arises from the fact that after a specimen has been 

 mounted in it, and has stood possibly for years, the jelly may 

 develop an unpleasant tendency to liquefy, as will be evidenced 

 by the presence of small beads of glycerine round the edge of 

 the cover-glass. Moreover, this seems to come about without 

 its being possible to track the cause of the mischief. Eor 

 instance, I have slides which were put up twenty years and more 

 ago, and which have never shown any signs of deterioration, 

 while others, which have lain side by side with these, and which 

 did not date back nearly so far, have had to be discarded as 

 failures. Some time ago I had the misfortune to lose a large 

 portion of my then small collection in the above manner, and 

 since then have constantly been on the look-out for indications 

 as to how such an occurrence could be avoided in the future. 

 While not being able, so far, to suggest any unfailing remedy, 

 I have come to the conclusion that there are, nevertheless, a 

 few simple rules the careful observance of which will consider- 

 ably minimise the risk of such a disappointing experience aa 

 that to which I have alluded. These are : — 



1. Care should be taken to remove the preparatory fluid 

 from the surface of the object, as far as possible, 

 before mounting. 



2. No pressure should be applied to the cover-glass iu 

 order to keep it in position, its own weight being alone 

 sufficient for the purpose. 



:i. A sufficient quantity of the jelly should be used to 



.•Uk)W of a small portion extending on every side 



beyond the edge of the cover -glass. 



4. The sUde should stiind for at least two or three months 



before the addit ional jelly is removed and the cell sealed, 



as this ensures the duo contraction of the jelly. 



.5. The slides should not be kept in a draughty position. 



During the past few years I have frequently used formalin 



in my mounts, and up to quite lately, with what seemed to be 



most satisfactory results. My modm operandi has been 



as follows : -While the shde is on the hot-water bath, with a 



small pool of melted jelly on it, ready to receive the object, I 



drop into the jelly, from the end of a thin glass rod drawn to a 



point, a drop of 4i* per cent, solution of formalin ; then 



quickly mix this with the jelly by the help of a dissecting 



needle, arr.uige the object and jilace the cover-glass in position. 



All these latter stops have to be carried out with considerable 



expedition, on account of the speed with which the jelly sets 



when oticc the formidin is added. After the slide has cooled, 



the jelly will be found to have solidified into a firm compact 



mass, and whereas in an ordinary mount a moderate degree of 



heat would suffice to re-melt it. now even soaking iu boiling 



water has no such effect. The binocular dissecting microscope 



