February, 1911. 



KNOWLEDGE. 



59 



the impression of the whole, which is tlie \\ork of 

 the well-known painter, Seitz, is an exceedingh- 

 pleasing one. The constellation Leo. in honour of 

 the late Pope, is not onl\- shown at its culminating 

 point, hut its i)rincipal stars are replaced In' minute 

 electric glow-lamps, so that their effect, when lighted, 

 is ver_\- charming. Hard by, in the \'atican gardens, 

 a surprise of a different kind, but also conceived in 

 honour of Leo XI IE awaits the visitor, in the shape 

 of a large open-air den containing the two magnifi- 

 cent lions presented to His Holiness bv the Emperor 

 Menelik. As in Rome itself, that city where of all 

 others the centuries ma\' be said to meet, and where 

 the works of wideK' distant ages unite in strangest 



famous grotto of LourdeS; Vs-ith its bubbling si>ring 

 of healing waters all complet'^ ! 



Father Hagen. however, has succeeded with 

 masterly skill in uniting t' ; various outlying 

 (Ifliartments nf his observator\ into one organic 

 whole. New instruments have bec-.i purchased, new 

 measuring appaiMtus introduced fc: the n-_asure- 

 ment of the asc. graphic plates (one of the chief 

 tasks of the obser\a*ii--\-), and new work it oa foot; 

 while the substitution of a spectrohelu -rj.ph, on 

 Professor Hale's s\-steni, for the existing ;;l'ioto- 

 heliograph will probably take place in the i-.e£.r 

 future. With so able an observer at the head c: 

 affairs, assisted as he is h\ the energetic cooperaaon 



FiGL'RI-: 4. 

 The Dome containin.^' the I'hotoheliograph. 



contrast, so in that portion of it represented b\- the 

 Pope's garden the juxtaposition of incongruities is 

 not wanting. Mention has already been made of 

 electricallv-driven oliservator\--domes and steel girder 

 bridges crowning the mig"ht\' bulwarks of a h\-gone 

 da}-, but this is not all. Midwa\' between the 

 observatories themsehes there rises the slender spire 

 of the chapel surmounting an exact replica of the 



FiGi-Ri: .T. 

 Ill this Dome is the Astrogrnphic Refr.ictor. 



of Fathers Lais and Stein, the \'atican Observator\-, 

 now fulh' reconstructed, and equipped with modern 

 appliances, has certainly entered upon one of the 

 brightest periods of its long career. The massive char- 

 acter of its foundations, the seclusion of its position in 

 the midst of the \'atican gardens, and the singular 

 fiurit\' of the Roman sk\' under which it works, all con- 

 s;)ire to render its obser\'ations of exceptional value. 



DRMOXSTRATIOX OF THE PRF.SE\XK OI^ .ST.XRrii IX .A I.KAF. 



Er is customarv tn Imld. in connection with the 

 Annual Meeting of the Association of Public School 

 Science Masters, an exhibition of scientific apparatus 

 and books likelv to be of use in science-teaching. 

 The show is divided into two parts, one consisting 

 of exhibits h\ members of the .\ssociation, and the 

 other of displays by opticians, instrument-makers and 

 scientific publishers. There was an exceedingly fine 

 exhibition at the January meeting, and the present 

 writer was particularh' interested in a modification, 

 devised by Mr, O. H. Latter, of Charterhouse, of 

 the usual experiment to demonstrate the presence of 

 starch in a leaf which has been exposed to sunlight. 

 For those who do not know the details, one may 

 say that a leaf is exposed to sunlight for some hours, 

 gathered, boiled in w ater for a few moments, and the 

 green colouring or chlorophyll, dissolved out by 

 means of methvlated spirit. In turn the alcohol is 

 washed out by water, and finally the leaf is placed 



in iodine solution, which turns the starch blue. 

 Although it is possible to get an intenseh- blue colour- 

 ation of the leaf, especially if a suitable one has been 

 chosen, and iodine dissolved in a solution of potassium 

 iodide has been used, as the writer can testify by 

 experience, Mr. Latter thinks that this method of 

 showing the leaf when in the iodine solution makes 

 a considerable demand upon the imagination: for he 

 describes the colour produced as a dull purple-brown, 

 that is, a mixture of the colour produced in the 

 starch with that in the other constituents of the leaf. 

 His plan is to remove the leaf from the iodine 

 and place it at otice in benzole. The benzole then 

 dissolves out the iodine from the cellulose walls of the 

 cells and from the protoplasmic contents, but does 

 not break up the blue starch-iodine compound. 

 Hence the blue colour shows up very plainh' in the 

 leaf, being no longer masked by the yellow-browns 

 of the iodine stained cellulose and protoplasm. 



