Notices respecting New Books. 383 



on the right is balanced by a weight, which is seen depending 

 on the left. The whole is surmounted by the bulb of air; and 

 the vacant space above the mercury upon the right is the Tor- 

 ricellian vacuum of the barometric column. Changes in tem- 

 perature are shown by this thermometer in the varying 

 angular positions of a needle, prolonged from one or other of 

 the radii of the wheel, and counterpoised by a piece of metal 

 on the other side. When the centre of gravity of this system 

 has been made coincident with the point on which it turns, the 

 liquid, under changes of temperature, is almost absolutely 

 motionless, whilst the tube which holds it moves. By bring- 

 ing the extremity of the needle into contact with a cylinder 

 driven by clockwork at an even speed, we have a thermograph 

 complete. Of course some delicate method of recording must 

 be used ; and I have hitherto employed the smoked-paper pro- 

 cess, so much adopted in the observatories of France. I 

 prefer to make my records on the albumenized paper prepared 

 for photographic use, and, for the sake of the beauty of the 

 black, to smoke it over the flame of a common tallow dip. I 

 then fix the records by immersing, cylinder and all, in lac 

 varnish diluted with methylated spirit. In this process there 

 is not the slightest danger of injuring the results ; and these, 

 when several times revarnished and mounted upon card and 

 rolled, are doubtless permanent, and are certainly incompa- 

 rably more beautiful than any other tracings I have seen. 



XLIV. Notices respecting New Books. 



Catalogue of Books and Papers relating to Electricity , Magnetism, 

 the Electric Telegraph, 8fc, including the Ronalds Library. Com- 

 piled by Sir Francis Eonalds, F.R.S. London : E. and F. N. 

 Spon, 



TN publishing this Catalogue the Society of Telegraphic Engi- 

 -*- neers have rendered invaluable assistance to those interested 

 in following the development of the science of Electricity. 



The Catalogue, with its 13,000 entries arranged in the alphabetical 

 order of the authors' names, and annotated to some extent by the 

 compiler, comprises nearly every contribution made to the science 

 in English, French, German, and Italian up to the date of 1873 ; 

 and we are glad to learn from the Preface that the Society contem- 

 plate completing the Catalogue by a Supplement. 



Originally undertaken as material for writing a history of Elec- 

 tricity, the collection of the books and compilation of the Catalogue 

 occupied Sir F. Eonalds during the latter years of his life; and it 

 is to be hoped that the great labour thus voluntarily incurred may 

 prove of some value to his successors. It was this hope that in- 

 duced him to leave his Library and Catalogue to the late Mr. Samuel 

 Carter, with the request that he would so dispose of it as best to 



