892 



NATURE 



fDECI 



|)iin< I 



, iIm- Mii 'A 



I, ' . In ,1 n . ■ ; ^ 



I print 

 oi , li, ■ t i. oiiii , llnrr 



fun '' , , .idlllllillilr riill- 



.ili lu the >ul>ji-rt. 

 11,, i,iitl\ W iilc 



ficl.l, ; •, ,i!.i,itiun. 



M\\ n, I .liiji mI niiiiii.i iplitiL'. 



cxplaiiiil I'Ui (il the iMiiiiiii.i 111 ii,i, i\.iii;|ii' m tlic 

 valuatimi nl i n.il ami iin-tallilcruu^ ihmk ^. and \alnatiiin 

 tor ^|)fi i.il |»urp(isi ii m-.: , i i' . ( luph i n.. 



rclatiiiL: to " Mineral i >( puMU. " i> pi rliap-> tin- \n>\ in 

 llif liiMik, the (McurniK f nt nnncrals luinL: .i suhji-ct 

 (il uliich i'rol. l,uuis \\\\-. had wide r\|ii ricnce and on 

 \vhi( h 111- lias written nun h. I'ndi i iliis head he 

 descrilK'S sinipl\ and with hiei(Ul\ tlie niaiini-r dt 

 occurrence of minerals in heds. \eins, and ina>>es, 

 infliratin-jT the \ariali(ins in |)uinl ut value tu which 



the\- are ^illijeet . 



His dissertatitin on llu' ■" prohahilitx' of error " in 

 the determinaliun ol the llii< kness ot deposits for 

 computation of the contents (( luqitc r iii.) is of much 

 interest ; but the method usually adopted by mining 

 engineers and alluded to by Prof. Louis on p. 50 is, 

 perhaps, as satisfactory as any other method, namely, 

 " after calculating average values as closely as the 

 available data permit ... to deduct a certain per- 

 centage ' for safety.' " The author is insistent, and 

 rightly so, on the impossibility of assigning " to any 

 mineral property an absolutely definite value, but 

 only a most probable value." Whilst this is particu- 

 larly true of a mineral property, by reason of the 

 variations in regularity of deposits, of selling prices, 

 and the general risks attendant on mining, it is of 

 course true also, to a lesser extent, of other things 

 as well, e.g. agricultural land, owing to the risks to 

 crops due to bad seasons, variation in selling prices, 

 etc. To meet the greater uncertainty of mines, 

 valuers allow in the computation of the value of the 

 annuities an unusually high rate of " remunerative " 

 interest. 



The debateable subject of subsidence of the surface 

 due to extraction of minerals (as to which a Royal 

 Commission, of which Prof. Louis is a member, is at 

 present inciuirinu) is touched upon, and the author 

 rightly says (p. 69), " It will be seen that we are still 

 very far from having arrived at anything like an 

 accurate estimate of the requirements in any given 

 case, and it will always be well to be guided by local 

 experience obtainable from previous workings when- 

 NO. 2825, VOL. 112] 



is avail.i' 



*'«venit.... 

 lies SO ni. 

 dii lory ri.->ults of diff< 



sldelK e lliis tlieiir\ liel; 



might, with 



of the dome 



i;,'ly contra- 



rvcr.'. rtKiirding sub- 



tT<( t lh;it in stratificrl 



il,-» iwse llie area u: i 



• '.e rn()\enu-nt din :,. 



Iiirth<r one ;.'i" 



The (|ue^tiun 1.1 <!rjni . la.t.l.i.'i i.l plaUl fUt' 

 mine \aliiati(ins; it. wv.v: . iiidfid. lie an in' 

 Item : an immense -um 



lor example, nt a dicp ni' ni' in;; tiie 



allnwanee tdf (|'-prei i:it inrt . i < s what 



netti'.d ; ' it 1^ charged 



eai;! ,eai i.p'ili uh' \ai;:< 'i| the plant IfhS tilt a' "' 



ol de[)reeiation written off \\^<- pn-vious vear 



says, seeiiiL' that the plant 



zero, and th.tt. under tlie n.-.i,-., ,,, .,,,,. ,-,~, ,,,, 



amount written off f^r de])reeialion is a maximum 



when the machinery is new and he^ 



as the maehinery u'cts older, the nai.;. 



The value of the phmt at tht tennination 



— if the jiropertv is leased — ol idur^e de])end.->, amongst 



other tliinu^. on whether the mineral> in the leasehold 



are t'xhau>ted or nut. and nil the ^ite nt the mine: 



and, on the seennd point, at a well-managed mine 



renewals of machinery and plant .ne ( arried out to a 



considerable extent durinu a I'n a a^e. which 



to some extent militates a::ainst Prui. Louis's criticism, 



though not entirii} . 



Chapter \-. treats of " lormulas and CaUul. 

 Why, by the wa\. dot- ' T mis prefer this plural 



to the one in eomnion rmulae," and, whilst 



on the subject of grammar. wh\ dues he ])refer " under 

 these circumstances " to " in these eireumstanres "' .'' 

 The formulae are mainly lho.se familiar to st".dents of 

 Hoskold's "Engineers' Valuing As>i tant 

 "Theory' of Finance." the latter heiiiL; tlu- ne-i ""ik. 

 known to the i)resent rexiewer. on the d"etrine tif 

 interest and annuities certain. The ex 

 forbid a detailed review of this secti-i. .1 v: 

 but it may be noted that the author directs at 

 to the necessity of makim: the projier and nee^.:^sa^y 

 deduction for income tax in tlie t aleul.ui"" »■"• 'he 

 recovery of capital. Likewise. • it the '>e 



invested in the purchase of mineral rights ... it he- 

 comes further liable to mineral rii'hts dni\- in accord- 

 ance with the Finance (loco-i .'" namely, 

 \s. in the pound. It is not uener.tll) realised what a 

 difference there is between the urt'ss and net income 

 derivable from the ownership of mineral lands ; mineral 

 rights duty heinu chargeable ajter the deduction of 

 income tax. 



