316 Chronicles of Science. [A.pril, 



the protiiLeranccs on tlie sim's disk in full sunshine, he describes 

 an ingenious plan by which he expects to be able to see the actual 

 prominences at any time. The principle consists in getting one of 

 the luminous Hues into the spectral field, and then rapidly rotating 

 the spectroscope. As the length of the luminous line depends upon 

 the height of that part of the protuberance which it represents, it 

 is evident that the rotation will cause the line to vary with the 

 different widths of the elevations; and if the rotation is suffi- 

 ciently rapid, the permanence of the impression on the retina will 

 produce an accurate representation of the protuberance under exa- 

 mination. 



AVhilst M. Janssen only suggests an ingenious method by which 

 these prominences may be seen, Mr. Huggins has actually suc- 

 ceeded in seeing them, as our readers will have seen from our 

 ' Chronicle of Astronomy.' 



A very beautiful experiment in spectroscopy has been described 

 by Dr. Wallner. He passes the rapid discharges of a Leyden jar 

 through an ordinary Geissler tube, and examines the light by 

 means of a spectroscope. If the length of the discharge is increased 

 a little, the sodium line immediately appears ; and with a proper 

 length of spark the brilliancy of the sodium line far exceeds that 

 of the spectrum of the gas. By further increasing the distance of 

 the discharge, the calcium line is produced with such intensity that 

 it cannot be seen to greater advantage by any other method known. 

 Finally, if the length of the spark is again augmented, the pheno- 

 menon changes, the light in the tube assumes a dazzling splendour, 

 this luminous line forms a continuous brilliant spectrum in which 

 the spectroscope reveals a completely black line instead of the 

 sodium line ; this, therefore, is the artificial production of a Fraun- 

 hofer line. 



Microscopists will read with interest a very simple method of 

 preserving animal specimens for fine dissection. It is described by 

 Dr, Alcock. The advantages of the plan are — very perfect preser- 

 vation ; no necessity for closing up, so that the specimen cannot 

 be got at ; no fear of losing a valuable dissection from accidental 

 evaporation, as where spirit is used ; lastly, cheapness. The method 

 adopted is to prepare a saturated solution of corrosive sublimate in 

 alcohol, and when a dissection in water is in progress, a small 

 quantity, as half-a-teaspoonful, of the solution is to be added from 

 day to day if the slightest appearance of putrefsiction is observed, 

 but no more of it is used than is absolutely necessary ; and by the 

 time the dissection is completed, the specimen lias become imperish- 

 able from the union of the corrosive sublimate with the tissues, and 

 it may then be kept in pure water, either open or mounted in the 

 usual way. 



