198 



Mr. E. Roberts. On a new Tide- Pr edict er. [June 19, 



respiratory curves appear in the tracing. The tops of the individual 

 beats in the tracing are sometimes flattened, sometimes rendered more 

 pointed ; this latter change is scarcely seen when ether is employed. 

 J^o very marked difference exists between the two agents as regards 

 their effects, but chloroform seems to have the more depressing effect 

 on the heart. The uncertainty of the results from both agents is 

 remarkable. 



The opinion is expressed that the curves apparent in many of the 

 tracings are not by any means solely the result of respiratory move- 

 ments, bat more often of deranged cardiac or arterial action. Experi- 

 mental tracings are given, showing the effects of forced inspiration 

 and expiration, and of the former when the subject had been pre- 

 viously in a state of semi-suffocation, and the blood, therefore, 

 detained in the right cavities of the heart. It is pointed out that the 

 occurrence of waves of contraction in the arteries, such as are seen in 

 the bat's wing, would account for the production of some of the 

 curves, especially those which exhibit the curious phenomenon of 

 diastolic ascent. The view is maintained that the occurrence of curves 

 in the tracing is a morbid sign. 



The tendency of narcosis to produce flattening of the tops of the 

 several beats is pointed out, and it is particularly observed that the 

 same change is marked in cases of fatigue of the heart. The heart's 

 force, and the arterial contractility are no doubt weakened in both 

 states — narcosis and fatigue — and this weakening is regarded as 

 accounting, together with the engorgement of the right auricle and 

 veins, for the flattened summit of the beat. 



XV. "Preliminary Note on a new Ticle-Preclicter." By 

 E. Roberts, F.R.A.S. Communicated by Gr. G. Stokes, 

 M.A., D.C.L., Sec.R.S., Lucasian Professor of Mathematics 

 in the University of Cambridge. Received June 12, 1879. 



The Indian Survey Department having undertaken the superinten- 

 dence of tide-registration around the whole sea-board of India and at 

 the port of Aden, and also the reduction of the observations by the 

 method of harmonic analysis, with the view to the prediction of the tides 

 for the whole of the ports, it became a matter of necessity, in order to 

 save the large outlay which the numerical operation of their prediction 

 would have involved, that an instrument should be constructed to 

 delineate the predictions. 



Accordingly, on the recommendation of the Surveyor- General of 

 India, Mr. Roberts was desired to design, and to undertake the con- 

 struction of, an instrument to include such a number of tide-corn- 



