Miscellaneous Intelligence. 165 
is to record the rates —— = with corresponding temperatures, 
in the graphic form of curv : 
The inconveniences - these two methods as ee to chro- 
sg on board ship 
must be gre 
2a and these differences will only appear with change of seasons. 
here must frequently occur, on board a cruising ship, inter- 
i Rei of the regular observations. 
(3.) In consequence of these interruptions the observations may 
be badly distributed on the scale of te — res 
(4.) Skill is necessary in the obser 
(5.) The a so dintaliaat ys dolicetéa 8 studied repre- 
sent only the Harbor rates, whereas the practical navigator is 
directly concerned with the ‘Sea rates, and it is well known that 
these — sometimes differ widely. 
igator on vr sereite these many and important a 
pectandad will be led justly to conclude that so much labor 
practically useless, rte will trust as implicitly to the veculation 
of his chronometers, as to ae demonstrations of a formula based 
on such uncertain condit 
It is proposed, therefore, ‘é apply the see not to the rates 
themselves, but to r diff erences, or what is the same thing to 
the second iocenton ‘of daily comparisons, _'These peieanes, 
psc every day; the interruptions in the observations will not 
occur; the observations will be better distributed on the eae of 
reeset talent of observation will not be necessary; two 
chronometers will be followed at once; and finally the perturba- 
tions of sea rates nef nd directly. 
There is one decided oe in this method, the impor- 
tance of which it is impossible to deny, viz: that the result 
practically useful to the navigator is the variation of the rate 
itself, which must still ve sought by the ordinary methods, because 
this method only furnishes the variation in difference of rate 
The ordinary methods mt however be facilitated by a study of 
the difference of rates, and are of themselves insufficient to pet 
the regularity of sea rates or the validity of the proposed form 
Since the rate of a oe may be regarded as a fanctioh 
of the two variables, time and temperature, it may be expressed 
= the ei po of a series (Taylor 8 aa and Mr. Yvon 
1 he . 
same tim 
Pa The eral properties of chronometer-rates are implicitly 
contained in the formula of Yvon Villarceau. The importance of 
