1865.] Physics. 693 



be added, no change will take place even after several days ; but if 

 blood which contains only oxygen in solution is treated with sulphide 

 of ammonium, an almost immediate change takes place, and only one 

 band is seen about midway between D and E. By this unchange- 

 ability of blood holding carbonic oxide in solution on the addition 

 of sulphide of ammonium, the author detects the presence of the 

 poisonous gas. It is worth quoting that the author has found that, 

 by continuing artificial respiration for a time, animals poisoned by 

 carbonic oxide have been restored to consciousness, the gas being 

 expired as carbonic acid. 



Mr. Gassiot has communicated to the Eoyal Society a description 

 of a rigid spectroscope, which he has had constructed with a view to 

 ascertain whether the position of the known and well-defined lines of 

 a spectrum is constant, while the co-efficient of terrestrial gravity 

 under which the observations are taken is made to vary. The idea of 

 it was suggested by Professor Tait and Mr. Stewart, and Mr. 

 Browning was consulted as to the practicability of constructing the 

 spectroscope. He considered such an instrument could be made, 

 with sufficient rigidity in all its parts, to examine with great accuracy 

 any given portion of the spectrum which might be selected, and for 

 which the prisms would have to be adjusted and fixed. The observ- 

 ations having been originally intended to be made in balloon ascents, 

 the construction of the spectroscope had necessarily to be considered 

 in reference to some portable and easily manageable form, and it was 

 particularly desirable that its weight should be as low as possible. 

 The instrument was completed so as to weigh little more than 40 lbs., 

 but it was soon found that the errors arising from changes in the 

 temperature were so variable, that no good results could have been 

 obtained in balloon ascents, where rapid fluctuations of temperature 

 would continually occur ; it was then determined to attempt the con- 

 struction of a rigid spectroscope, with which observations might be 

 made, either on board a vessel or on land in various latitudes, and as 

 the question of the total weight of the apparatus became no longer of 

 paramount importance, an alteration in the construction of the instru- 

 ment was decided upon. •Three large prisms are used, with sides 

 2^ inches high and 3 inches long, the light being reflected back through 

 them, so as to make the whole equal to that which would be produced 

 by five prisms if employed in the ordinary manner. Thermometers 

 were inserted into holes drilled in the prisms, so that the exact 

 temperature of these and also of the surrounding atmosphere can be 

 taken. The performance of the instrument is very satisfactory ; Mr. 

 W. Huggins has seen two bright lines between the D lines produced 

 by the flame of a common spirit lamp ; and several persons have seen 

 on different occasions from five to seven lines between the D lines in 

 the solar spectrum. This is equal to the performance of the large 

 spectroscope, with which the solar spectrum is now being mapped at 

 Kew Observatory. Numerous observations of the different readings 

 of one of the D lines for variations of temperature are given, and the 

 result of observing under a varied temperature of 40° Fahr., the 



