and twelve inches deep, respectively, the amount of phosphoric 
acid present increases with the depth at which the sample is taken, 
and it is possible therefore that at still greater depths material 
richer in phosphoric acid than the best of these samples may be 
obtained. 
COMMERCIAL VALUATION. 
Samples of the four guanos were submitted to dealers in guano, 
who were also informed of the results of their chemical examination, 
for commercial valuation. They stated that large deposits of bat 
guano occur in Mexico, Borneo, Algeria, Jamaica and elsewhere, 
and that small consignments, similar in composition to those now 
sent from the Federated Malay States, had occasionally been sent 
to this country, but that the material had not been received with 
favour, and there was reason to believe that these shipments had 
not proved remunerative to the exporters, and as a result no regular 
trade in this product has become established. The Imperial Insti- 
tute will be glad to supply any further information regarding 
methods of utilising these products which may be required. 
WYNDHAM R. DUNS FAN. 
23 rd June , 1905. 
IMPERIAL INSTITUTE. 
(SOUTH KENSINGTON, LONDON, S. W.) 
REPORT ON SAMPLES OF PATCHOULI AND 
CITRONELLA OILS FROM PERAK, MALAY 
PENINSULA. 
BY 
Professor Wyndham R. Dunstan, m.a., f.r.s., Director . 
These two samples of Volatile oils were forwarded to the Impe- 
rial Institute by Mr. W. K. Smith, of the Kellas Estate, Perak, 
together with a letter dated the 21st December, 1904, at the sug- 
gestion of the Superintendent of the Botanic Gardens, Singapore, 
and it was requested that they might be examined and their quality 
and commercial value ascertained. 
CITRONELLA OIL. 
Description of Sample. 
The sample measured about four fluid ounces and was labelled 
“ Citronella Oil, distilled on the Kellas Estate, 20th December, 
1904.” The oil was of a pale yellow colour and possessed the 
characteristic fragrant odour of citronellal ; it was quite clean and 
free from water. 
Chemical Examination. 
The oil was chemically examined in the Scientific and Technical 
Department of the Imperial Institute, and gave the results recorded 
in the following table, which also gives, for convenience of com- 
