118 Compensation for Unexhausted Afanurial T alues. 
expected to yield a benefit for a longer period, and we have 
lengthened their duration accordingly. Dissolved bones are 
more rapid in their action, and so a higher proportion has been 
put down as being taken up by the first crop. Regarding basic 
slag, a long series of statistics exist, notably those from the 
Cockle Park Farm of the Northumberland County Council. 
While basic slag is. not so certain in its action on arable land, it 
is clear that, where it is well suited to grass land, the benefit 
may last for seven to eight years. 
Bone and compound manures are very variable in composi- 
tion, and it is with these that one meets with most cases of 
comparatively high prices being charged ; we think ourselves 
justified, therefore, in putting these into a lower scale as 
regards their residual value than superphosphate or dissolved 
bones. 
It may again cause some surprise that the effect of nitro- 
genous manures such as Peruvian guano, fish guano, and meat 
meal, is reckoned to be so readily exhausted ; but this is what 
the experience of the Rothamsted Experiments in Little Hoos 
Field has shown. The same applies even more strikingly to 
manure-cakes and dried blood. It will, however, cieate no 
surprise to those who have followed the Rothamsted and 
Woburn Experiments, that we allow no appreciable residue 
in the case of nitrate of soda, sulphate of ammonia, or the 
more recently introduced nitrogenous fertilisers, cyanamide, 
nitrate of lime, &c. 
Potash salts, however, possess a longer duration in the 
soil, and hence we reckon them to last through to the thiid 
crop. 
Lastly, as regards lime, we have clear evidence from the 
Woburn Experiments that, on arable land, lime, when required, 
will exercise tangible benefit for quite seven years, and, on 
grass land, may be expected to last even longer. 
In drawing up these new Tables, we. have been actuated 
solely by the desire to put the system of valuation of unex- 
hausted residues on as scientific a basis as possible, while 
having due regard to practical considerations. We know 
well the imperfections of our own knowledge of the subject, 
but, so far as the results of actual experiment are available, we 
have endeavoured to utilise these for the purpose of drawing 
up our Tables. We in no way, however, wish it thought that 
we are proposing to dispense with the Valuer, for, as our Paper 
will have shown, there are numerous points in which the 
judgment of the Valuer must be exercised, and our Tables are 
intended primarily to give him a sound basis upon Avhich to 
work. 
