230 Royal Society : — 



Examples : — 



Zinco-sulphate. Magnesia sulphate. 



Sodic sulphate. Ammonia phosphate. 



It will be seen that the sodic sulphate and the magnesia sulphate 

 also occupy a place in Class I. 



V. Anhydrous salts examined in this memoir that do not form 

 supersaturated solutions : — 



Potassic nitrate. 

 Potassic bichromate. 

 Sal-ammoniac. 

 Sodic nitrate. 

 Potassic chlorate. 



Potassic ferrocyanide. 

 Baric nitrate. 

 Plumbic nitrate. 

 Ammonium nitrate. 



" On the Tides of Bombay and Kurrachec." By William Parkes, 

 M. Inst. C.E. 



The object of this paper is to exhibit the phenomena of diurnal in- 

 equality in the tides on the coasts of India, and describe the mode 

 adopted by the author for obtaining formulae based on astronomical 

 elements for predicting them. It is accompanied by the following- 

 records of observations, given in a diagram form : — 



Kurrachee, 1857-8, December to March. 



,, 1865, March to August. 



„ 1867, The whole year. 



Bombay 1867, February to May. 



The height and times predicted by the author for 1867, and 

 published by the India Office, are given on the diagrams for that 

 year, so that they may be compared with actual observation. 



The continuous curves of the height of the water taken at Bom- 

 bay, at every ten minutes for the four months above named, are also 



§ iven - 



By the rotation of the earth every meridian-line is brought twice 



a day under the influences which ultimately result in the well-known 

 semidiurnal tidal movements — once when in the position nearest to 

 the attracting body, and once when in that furthest from it. But 

 the actual point in that meridian which is in the centre of those in- 

 fluences will be alternately north and south of the equator, to the 

 extent of the declination of the attracting body. This alternation 

 of the position of the centre of attraction from the northern to the 

 southern hemisphere produces a diurnal tide, and that diurnal tide 

 produces a diurnal inequality in the semidiurnal tide. 



The character of the diurnal tide and the highly complex con- 

 ditions under which its constantly varying solar and lunar component 

 parts are combined are then traced. Being entirely dependent on 

 the declinations of the sun and moon, the solar element vanishes 

 twice a year, and the lunar element twice a month, each reappearing 

 after the solar or lunar equinox, with its times of high and low water 

 reversed. 



The diurnal tide produces a diurnal inequality in height and time 

 of high and low water, affecting simultaneously respectively high- 

 water time and low-water height, and high-water height and low- 



