TO CORRESPONDENTS. a 
, ed ad 
“Mancetxus’s difficulty arises from confounding the present value of a rever-- 
sionary annuity, with that of an equivalent reversionary swnt:—the former is at q 
worth one year’s purchase more than the latter, because both becoming due at _ 
the same period, the annuity is receivable at the commencement of the year, when | 
the corresponding sum (if invested) is only beginning to be productive, and on — 
which an annuity, equal in amount, will not become due until the end thereof.— 
For further information on the subject, we recommend M. to peruse with atten- ~ 
tion the whole of Prob. 23, chap. 6, and Questions 26 and 27, chap. 12, of 
Barty’s Doctrine of Life Annuities. 
PHARMACOPGIA LONDINENSIS, 
Iterum recognita et retractata, 1824, p. 6. 
“ ACIDUM ACETICUM FORTIUS,” 
vel 
“ Acidum Aceticum 2 Ligno destillatum.” 
URE CONCENTRATED ACETIC ACID, agreeable to the Sample 
furnished at the request of the Committee of the Royal College of — 
Physicians, may be had of the Manufacturers, BEAUFOY & CO. South 
Lambeth, London. 
ENGRAVINGS IN THE PHILOSOPHICAL MAGAZINE, 
illustrative of the following Subjects: 
Vol. LIII. 1. Dr. Ure’s Experiments on Caloric, Mr. Luckcocx’s 
Paper on the Atomic Philosophy, and Mr. Botron’s on the Purification 
of Coal Gas.—2. Mr, Rennir’s Apparatus employed in his Experiments 
on the Strength of Materials; and the Marquis R1poLpui’s Improvement 
on the Gas Plowpipe.-5. Mr. Merxte’s Paper on Calorific Radiation ; 
Mr. Lowe’s on the Purification of Coal Gas ; and Mr. Hugurs’s on ascer- 
taining Distances—4, Dr. OLinruus Grecory’s Paper on the different 
Rates of PennincTon’s Astronomical Clock at the Island of Balta, and at 
Woolwich Common, 
Vol. LIV. 1. Menai Bridge.—2. Mr. Lowe’s Mercurial Pendulum.— _ 
3. Mr, Hare's Calorimotor, a new Galvanic Instrument.—4. Capt. Sa- 
BINE’s Illustration of Irregularities observed in the Direction of the 
Compass Needles of the Isabella and Alexander; and Mr, ScorEsBy’s 
Anomaly in the Variation of the Magnetic Needle. 
Vol. LY. 1. Comet’s Path of July 1819.—2, Annular Eclipse of the Sun 
Sept. 7.—3. Mr. Lane’s Instrument for gathering Fruit; Mr. Young's - 
Mode of preparing Opium from Papaver somniferum; and Captain For- 
mMANn’s Essay on a Property in Light.—4. Mr. Curnserr’s Hydro-pneu- 
matic Apparatus, &c.—5. Capt. Forman’s Essay on the Reflection, &c. 
of Light ; Mr. C. Bonnycasrxe on the Influence of Masses of Iron. onthe — 
Compass. ; . 
Vol. LVI, 1, Mrs. Inserson on the Physiology of Botany.—2. Mr. : 
HA.v’s Percussion Gun-Lock; Dr, Krrcuener’s Pancratic poe 
Mr. Parx’s Mooring Blocks—3, Sections of Mr, MALAM’s 
4. Discoveries df Captain Parry in the Polar Sea. . 
as-Meter. A 
Bee 
