1874.] Physics. 533 
in effe@t a derived ele@trolytic circuit to the first. Should the experiments (and 
they are most carefully recorded) stand the test of general experience, the 
sequence of great importance in the practical deposition of metals would 
appear to follow naturally and immediately. 
The experiments were repeated with a magneto-eleftric machine, with 
results precisely similar to those obtained with the battery. 
The electric current has again been utilised for the purposes of ascertaining 
longitude, this time of Harvard observatory. The results show the difference 
of time between Harvard and Greenwich to be for the following years :— 
Hrs. Mins. Secs. 
IGS167) Go you) ote sop 4 44 31°00 
WSO. ag hd vod. po 4 44 31°05 
UT 56 folo 4 Boe OC 4 44 30°99 
The mean of which is 4 hrs. 44 mins. 3r‘or secs. The close agreement of 
these results indicates a very near approximation to the truth, and this funda- 
mental longitude may now be considered as settled. Adding to the above 
value the difference in time between the Washington and Harvard observatories, 
23 mins. 12°12 secs., we get for Washington 5 hrs. 8 mins. 12°12 secs. 
In America interesting le@ures upon the system of fire, burglar, and other 
alarms as laid down by the American Distri&t Telegraph have been delivered. 
Particulars will be found in the ‘‘ Journal of the Franklin Institute.” 
In natural science electricity has again made progress. Dr. Burdon- 
Sanderson has investigated the ele&trical phenomena which accompany the 
contractions of the leaf of Dionea muscipula, and he has demonstrated their 
collateral character with those of nerve and muscle. 
INVESTIGATION OF THE FLUORESCENT AND ABSORPTION SPECTRA OF THE 
URANIUM SALTS.—President Morton and Dr. Bolton, after briefly noticing 
the labours of their predecessors in this department of research, describe the 
methods employed, which do not differ from those of Stokes and Becquerel, 
except in small details, and the means at their disposal for securing accuracy 
in the measurements.' A variety of uranium compounds were specially pre- 
pared, and their spectra, both of fluorescence and absorption, were carefully 
mapped out and measured. Illustrations are given showing some of the most 
charaéteristic of these spectra. Very charaéteristic differences were found 
between the spectra of certain salts, and in a number of cases one body can 
be readily discriminated from another by this means. Indeed,inthis investiga- 
tion impurities in many commercial compounds of uranium were thus detected, 
and, in other cases, the progress and consummation of achange in composition, 
or in the formation of a compound, was watched and recognised with the 
greatest ease and precision. In almost every case there is a tendency of the 
light to fade off in the bands towards one side more gradually than towards 
the other. In nearly all spectra this graduation is greatest towards the less 
tefrangible end of the spetrum. The character of any one band is, as a rule, 
a type of all the bands of a spectrum; but to this a remarkable exception is 
found in the double acetates of uranium generally, and especially in the 
sodium salt whose fluorescence is the brightest. In the speétrum of this salt 
the first four bands at the lower end of the speétrum in the orange and red 
differ entirely in chara@er and spacing from the rest, except the fifth, which 
seems to be in a transition state. It is also true, as a rule, that double salts 
with the same acid have bands of a like charaf&ter; but to this also there are 
decided exceptions, and it is by no means true that all salts with the same 
acid have like bands. This chances to be true in the case of the sulphate and 
normal double sulphates, but in the case of the acetate and double acetates, 
fluoride and double fluorides, chloride and double chlorides, as also among the 
numerous hydrates of the sulphates, it fails to maintain itself. Nothing 
could well be more unlike than the spe&ra of uranic oxychloride and the 
potassium chloride. The question arises, how far the spectra of substances 
are constant, and in what way a change of spectra is to be interpreted. The 
authors find that no substance has its spectrum changed by anything which 
does not affect its composition, excluding the effe@& of heat, and certain cases 
